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Ramblings

Aperture, f-ratios, myths, etc.

Q: F-ratio myth - Myth, reality, or what? Does aperture always rule?

A lot has been written and discussed on the web about what f-ratio really means for us as astrophotographers. F-ratio is simply the ratio of the focal length to the size of the aperture. So, if you have a 200 mm telescope that has a focal length of 1000 mm, it is an f/5. This is true for your telescope and for your camera lens. Clearly, the f-ratio can be varied by changing either the aperture or the focal length. If we stick a focal reducer or a barlow on the scope, we’re changing the f-ratio of the system (Note: not of the objective itself, so sticking a barlow on your f/4 Newt to make it f/8 won’t make the coma of an f/4 go away!). Likewise, when the iris inside your camera lens cuts down the light (reduces the aperture) you’re changing the f-ratio.

If we keep the aperture constant and change the f-ratio by somehow scaling the focal length (reducing or extending it), we’re not changing the total number of photons hitting our detector from a given DSO. As Stan Moore and others have pointed out on pages like the one dedicated to the “f-ratio Myth”, it is the aperture alone that determines how many photons we gather from a DSO. If you imagine your scope to be a bucket, catching photons streaming across space, it should be obvious that the bigger a bucket you have, the more photons you get. Period. No ifs, ands, or buts as it were.

I feel Stan does a good job on his page explaining how film differs from CCDs and where the noise comes from. But, in seeing how this is often depicted in online discussions, I feel one key caveat he makes is often lost. Note that at the end of his page, he says that, “There is an actual relationship between S/N and f-ratio, but it is not the simple characterization of the ‘f-ratio myth’.” What is missed by many when they conclude that “f-ratio doesn’t matter” is that this is true ONLY when you are well above the read noise.

Running at a larger f-ratio for a given aperture means that you are spreading the light over more pixels. Thus, each pixel is getting less light and so the signal hitting that pixel is less. Some aspects of the noise (e.g., read noise) will be constant (not scale with the intensity of the signal the way shot noise does). Thus as the signal gets very faint, it gets closer and closer to the read noise. When we hit the read noise, the signal is lost. Doubling the focal length (one f-stop) will have 25% as much light hitting the CCD well, meaning we will be that much closer to the read noise. If the exposure length is long enough such that the edges of our galaxy or nebula are still well above this noise, it matters little if at all. But, if we are pushing this and just barely above the noise (or if our camera has a good bit of noise), this will more rapidly come into play.

Please note, that none of what I am saying here contradicts Stan’s message. He makes this same point and if you look closely at the images on his site, the lower f-ratio shot does appear to have less noise. As noted, it’s not “10x better”, but it’s not the same either.

Here, I’ve taken some data from Mark Keitel’s site. Mark was kind enough to post FITS files of M1 taken through an FRC 300 at f/7.8 and f/5.9. I ran a DDP on the data and used Photoshop to match black and white points and to crop the two frames. Click on the thumbnail for a bigger view and/or just look at the crop.


Here is a crop around the red and yellow circled areas. In each of these, the left image is the one at f/7.8 and the right at f/5.9 (as you might guess from the difference in scale. Now, look carefully at the circled areas. You can see there is more detail recorded at the lower f-ratio. We can see the noise here in the image and that these bits are closer to the noise floor. Again, the point is that it’s incorrect to say that the f-ratio rules all and that a 1” scope at f/5 is equal to a 100” scope at f/5, but it’s also wrong to say that under real-world conditions, it’s entirely irrelevant.


Q: Does aperture always rule?
The most often quoted phrase in our community is that aperture rules and it’s true. It’s true that if all else is equal, bigger scopes will do better. It’s also false to say that big scopes are bad on planets or bad in the city and that smaller is better under these circumstances.

However, there are times when we don’t fully realize what’s not equal. This point was made clearly to me recently when I went out to do some testing on a camera and brought along an 8” f/5 Antares Newtonian (with Paracorr) and a 4” f/4 Borg 101 ED APO. I aimed, among other things, at the Horsehead Nebula and thought I had a good handle on what the images would show me. I thought, as most of you probably would, that the 8” Newt (1000 mm focal length) would spank the 4” APO (400 mm focal length). After all, the Newt gathers 4x as many photons as the APO. I went in thinking less about the caveat to the f-ratio myth than I should have though, and given this, the results were quite surprising.

These are taken right after each other and are both 5 minute frames, with no application of any post-processing other than simple stretching (data from QSI 540). You can click on the image for a 100% version of the shot here.


I don’t know about you, but I’m seeing more detail in the 4” scope than in the 8” scope. The bit of emission nebula by the horse’s mane is one area you can pick this out. Whether you think the 4” is better than the 8” here might be debated (I don’t think so, but some might) but what we can certainly say is that the 4” wasn’t put to shame in this comparison. Despite giving up “4x the number of photons”, it is doing very well.

Why?

Is it some “APO magic”? Hardly. The answer, IMHO, comes down to two factors:

1) Much of the signal we’re pulling out here is close to the noise floor and, by having a lower f-ratio (and shorter focal length), the 4” APO is getting more photons onto the CCD wells as a result, getting us into the “caveat” range of the f-ratio myth.

2) There is more light loss in the Newt than we might expect.

Let’s put some quick and dirty numbers onto these images and pretend we’re imaging a flat field (e.g., the emission nebula around the Horesehead). What do we have here? Well, if the aperture were the same and we’re running one at 1000 mm and one at 400 mm of focal length, we can figure the difference in photon number hitting the well by (1000 / 400) ^ 2. This is a factor of 6.25. So, if we took a 1000 mm scope and reduced the focal length to 400 mm, each CCD well would be hit with 6.25x as much light. Again, this won’t matter a lot for brighter areas, but when you’re right near the noise, this will certainly come into play.

The aperture isn’t the same, of course, and the 4” scope is collecting 25% as many photons as the 8” scope, owing to the difference in aperture. So, if we’re counting the number of photons from a diffuse source hitting the CCD, that 6.25 factor goes down to 1.56x. But, that is still in favor of the 4” APO. Note, if this were a 3” APO, the light loss due to aperture would be down to 14% of the 8” scope, which would put the photon count hitting each well at a factor of 0.88, now tipped to the Newt’s favor.

All this is still pretty close and I don’t think enough to account for the images. Here’s something we’ve not considered yet, however. The Newt uses two Al-coated mirrors and several lenses in the Paracorr. The APO here is a doublet with several more lenses in its reducer / corrector. If we suppose that the two correctors loose similar amounts of light, we’re left with two mirrors vs. a doublet. That doublet is passing on the order of 97% of the light, but each surface of the Newt is only passing about 86% of the light. With two mirrors, we’re down to about 76% of the light. We’re also not at an effective 8” of aperture in terms of photon gathering owing to the central obstruction (about 2.5” here). The central obstruction alone puts us down to a 7.6” scope and if we factor in the mirrors’ light loss it’s down to a 6.6” scope. So, rather than an 8” vs. 4” scope with a 4x total photon boost for the 8”, it’s more like a 6.6” scope which is only a 2.75x total photon boost.

Now, if the total photon boost is only 2.75x instead of 4x (aka, the light throughput on the 4” scope is 36% of the bigger scope instead of 25%), we can update the numbers from above. Ignoring the aperture (keeping it constant), the focal length had 6.25x as many photons hitting the CCD well and getting us above the noise. With perfect optics, the light cut was 1.56x (6.25 * 0.25), but it’s now at 2.27x with more real-world numbers. That means that each pixel recording the nebula is getting 2.27x as many photons hitting it when the 4” scope is attached as when the 8” scope is attached.

Math, math, math... does this really happen? My camera’s bias signal is about 209 in this area. I measured the mean intensity in a 10x10 region using Nebulosity’s Pixel Info tool for three areas right around and in the Horsehead. On the Borg, they measured 425, 302, and 400. On the Newt, they measured 287, 254, and 278. Now, if we pull out the 209 for the bias signal we have 216, 93, and 191 vs. 78, 45, and 69. If we calculate the ratios, we have 2.76x, 2.07x, and 2.77x. Average these and we’re at 2.5x.

The back-of-envelope math said I should have 2.27x as much light hitting each CCD well with the 4” scope all things considered and the practical measurement came up with 2.5x. In my book, that’s close enough for jazz and a clear verification of the basic idea. Aperture did not win here. When all else is equal, it wins, but all else is not always equal. To my eye, the image with the 4” looks better and we find that despite seeming to be a bit light in the photon department when all one considers is aperture, it’s actually pulling in more photons onto each CCD well. While it has fewer photons on the whole target still (36% of the 8” scope’s amount), per CCD well it’s doing better. If aperture were all that mattered and that focal length didn’t matter at all, the 8” would have soundly trounced the 4”.

Must this be the case? Will a 4” APO always beat out an 8” Newt? Hardly. If we run them both at the same focal length, the APO won’t have a chance. Only 36% of the photons are now spread out to the same image scale and so each CCD well has only 36% as many photons hitting it. The Newt will clearly win here. Now, keep in mind, that if aperture were all that mattered, the 4” would have handily lost the competition above. It didn’t. Put them on par on image scale and it will.

This last bit is really the key for people to understand. What aperture buys you are more photons. You can trade these photons off in various ways. If you keep the image scale the same, your SNR will go up relative to a scope with a smaller aperture. If you like, you can trade things off here and buy magnification (aka resolution) for that aperture and keep the same SNR. By varying the focal length (and therefore image scale and f-ratio) we control this trade-off.

And yes, it is true, that once we’re well above the read noise, the effects I’ve mentioned here become weaker. But, a lot of the things we amateurs try to do aren’t always well above the read noise. I know I’m often plumbing the depths to see just what I can pull out. Just as we shouldn’t look only at the f-ratio when making our decisions and think that we can shoot for a quarter as long given a 2-stop difference (e.g., f/8 to f/4) we shouldn’t entirely ignore this. In addition to easing guide constraints and getting a wider FOV, running that f/10 SCT at f/6.3 or so will let you get above that read noise faster.





Astrophoto Insight & Astronomy Technology Today

Some of you may have seen articles and reviews I have done in Astrophoto Insight, Astronomy Technology Today, and Cloudy Nights (you can find these on the Articless and Reviews section of my personal page). I consider these three of my favorite astro-resources. Toss in the various Yahoo Groups and you’re set as far as I’m concerned. While the Yahoo groups and Cloudy Nights are free websites, Astrophoto Insight and Astronomy Technology Today both involve subscriptions for full access. Now, these aren’t break-the-bank kinds of prices. Astrophoto Insight will let you download the current issue for free and wants $24.95 for a “Platinum” level membership that will give you full access. Astronomy Technology Today wants $18 (for US print + online or for International online access). My advice - subscribe to both.

I subscribe to both and I do so not just because I’ve published in them or met the guys who run them. Sure, Al from Astrophoto Insight and Stuart and Gary from Astronomy Technology Today are all stand-up guys. These things and $1.69 get you a cup of coffee, not a wallet opening for a subscription, though. I subscribe because they publish solid articles on things I want to read about. From real tips and techniques to solid reviews, both do a bang-up job. And please, I’m not talking about my reviews and articles in here. I certainly skip those and can read them for free. When the latest issue of either comes out, I devour it. I devour it in the way I used to devour S&T years ago.

“Oh, but magazines are driven by ads” one might say. Sure, that’s a part of it. I’ve got a very long history with magazines and reviews as I grew up in the business (my father was a magazine editor). Ads give the magazines a lot of the money they need to do what they do but this can present a conflict of interest. So far, I’ve not detected biases in the reviews that would suggest the reviews are being slanted based on ad money. As someone who’s written for both, I can also state that I’ve been able to freely talk about the downsides of gear in my reviews. To me, that’s huge. Any product will have its good sides and bad. Some have more good and some more bad. To trust a source, you’ve got to know that when there are bad sides, they’ll be covered and not swept under the rug. Seeing both from the inside has made me feel I can certainly trust both. (FWIW, the more common thing to have happen is that when a product is really bad, it just won’t get reviewed. No, I’ve not hit that yet with either, but I did see it a bit growing up.)

Ads also do things for readers (apart from helping the magazine exist). They let us see neat new toys and find out new things going on in our hobby. Just a few days ago after seeing an ad in one of them I said, “Hey, that’s a cool new gizmo!” and contacted the company for more info. Depsite spending a lot of time with this hobby (far too much my wife would say), I’d missed this new gizmo (just so you don’t think I’m making this up, it was the Moonlight Telescope’s SCT focuser that lets you screw the focal reducer into the drawtube.)

There’s another thing that these two magazines do for readers when it comes to ads. They show ads for products that can’t make it into the bigger magazines. I certainly know this from first-hand experience. Our hobby has big companies and small companies and the small ones have certainly done a lot for our hobby too. Small ones often can’t afford to advertise in bigger magazines but can potentially afford to advertise in API and ATT. Or, even if they could, the ad wouldn’t have as much info in it as it’d be crammed into a small space.

If you’re not a subscriber / haven’t checked them out, do so. Heck, if somehow you’re reading this and don’t know about Cloudy Nights, stop reading this and get over there now. We’ve got some fantastic sources of information and communities available to us. Use them. Support them.

Craig

Gain, Offset, and Bit Depth

Q: What should I set my "gain" and "offset" to?

Before answering this, a bit of background is useful. Specifically, just what the heck do gain and offset do? Before we cover this, a brief primer on how those photons you capture become intensities you see on the screen is needed. If you wish, skip down to "OK, so what should I set my gain and offset to?" below.

How do signals off my CCD become intensity values?
When each CCD pixel is read out, there is a certain amount of voltage corresponding to how many photons were collected and converted into electrons. This is an analog signal that needs to be converted into a digital signal so that we have a number corresponding to the intensity. This conversion happens in the analog to digital converter (ADC). In so doing, we have a specification often seen on cameras, the overall system gain, typically specified as some number of electrons per ADU (analog-digital-unit, aka the raw intensities you see in your image in a program like Nebulosity). A camera may have an overall system gain of something like 0.7 e-/ADU or 1.3 e-/ADU, etc. This means that each electron registered corresponds to 0.7 or 1.3 raw intensity units.

There are four key limitations to keep in mind when thinking about the ADC process:

1) There are no fractional ADU outputs. So, one electron in both the systems above would probably end up recording 1 ADU. You can't have half an ADU (and you can't have half an electron).

2) Your ADC has a minimum value of 0 and a total number of intensity steps of 2 ^ (# bits in your ADC). For a 16-bit ADC, this is 0-65,535. For an 8-bit ADC, this is 0-255, etc.

3) Zero is evil and 65,535 is bad but not evil. When your signal hits either, you loose information. If the sky is at zero and your faint galaxy is at zero, no amount of stretching will bring it back. 0*1 = 0*100 = 0.

4) Your CCD has a limited number of electrons it can hold called the well depth. This may be 20,000 e-, 40,000 e-, etc. Note, that for all the cameras I know of that let you adjust the gain and offset (Orion Starshoot, Meade DSIs, QHY cameras, etc.), the well depth is < 65,535. This will be key for my argument below.

What do gain and offset do?
With all this in your head, we can now describe what gain and offset controls on cameras do. After coming off the CCD and before hitting the actual ADC there is typically a small pre-amplifier (this may be inside the ADC chip itself). What this preamp does is allow you to boost the signal by some variable amount and to shift the signal up by some variable amount. The boosting is called gain and the shift is called offset.

So, let's say that you have pixels that would correspond to 0.1, 0.2, 1.1, and 1.0 ADU were the ADC able to deal with fractional numbers. Now, given that it's not, this would turn into 0, 0, 1, and 1 ADU. Two bad things have happened. First, the 0.1 and 0.2 have become the same number and the 1.1 and 1.0 have become the same number. We've distorted the truth and failed to accurately represent subtle changes in intensity. This failure is called quantization error. Second, the first two have become 0 and, as noted above, 0 is an evil black hole of information.

Well, what if we scaled these up by 10x before converting them into numbers (i.e., we introduce some gain)? We'd get 1, 2, 11, and 10. Hey, now we're getting somewhere! With gain alone, we've actually fixed both problems. In reality, the situation is often different and the ADC's threshold for moving from 0 to 1 might be high enough so that it takes a good number of electrons to move from 0 to 1. This is where injecting an offset (a DC voltage) into the signal comes in to make sure that all signals you could possibly have coming off the CCD turn into a number other than zero.

Gain's downside: Bit depth and dynamic range
From the above example, it would seem like we should all run with lots of gain. The more the better! Heck, it makes the picture brighter too! I often get questions about this with the assumption that gain is making the camera more sensitive. It's not. Gain does not make your camera more sensitive. It boosts the noise as well as the signal and does not help the signal to noise ratio (SNR) in and of itself. Gain trades off dynamic range and quantization error.

We saw above how it reduces quantization error. By boosting the signal we can have fractional differences become whole-number differences. What's this about dynamic range?

Let's come up with another example. Let's have one camera with a gain of 1. So, 1 e-/ADU. Let's have another run at 0.5 e-/ADU. Now, let's have a pixel with 1k e-, another with 10k e-, another at 30k e-, and another at 50k e-. In our 1 e-/ADU cam, we of course have intensities of 1000, 10000, 30000, and 50000. In our 0.5 e-/ADU cam, we have intensities of 2000, 20000, 60000, and 65535. What? Why not 100000? Well, our 16-bit camera has a fixed limit of 65535. Anything above that gets clipped off. So while the 1 e-/ADU camera can faithfully preserve this whole range, the 0.5 e-/ADU camera can't. Its dynamic range is limited now.

How do manufacturers determine gain and offset for cameras that don't allow the user to adjust them?
Let's pretend we're making a real-world camera now and put in some real numbers and see how these play out. Let's look at a Kodak KAI-2020 sensor, for example. The chip has a well-depth specified at 45k e-. So, if we want to stick 45,000 intensity values into a range of 0-65,535, one easy way to do it is to set the gain at 45,000 / 65535 or at 0.69 e-/ADU. Guess what the SBIG ST-2000 (which uses this chip) has the gain fixed at... 0.6 e-/ADU. How about the QSI 520ci? 0.8 e-/ADU. As 45k e- is a target value with actual chips varying a bit, the two makers have chosen to set things up a bit differently to deal with this variation (SBIG's will clip the top end off as it's going non-linear a bit more readily), but both are in the same range and both fix the value.

Why? There's no real point in letting users adjust this. Let's say we let users control the gain and they set it to 5 e-/ADU. Well, with 45k e- for a maximum electron count at 5 e-/ADU, we end up with a max of 9,000 ADU and we induce strong quantization error. 10, 11, 12, 13 and 14 e- would all become the same value of 2 ADU in the image, loosing the detail you so desperately want. What if the user set it the other way to 0.1 e-/ADU? Well, you'd turn those electron counts into 100, 110, 120, 130, and 140 ADU and wonder just what's the point of skipping 10 ADU per electron. You'd also make 6553 e- be the effective full-well capacity of the chip. So, 6535:1 would be the maximum dynamic range rather than 45000:1. Oops. That nice detail in the core of the galaxy will have been blown out and saturated. You could have kept it preserved and not lost a darn thing (since each electron counts for > 1 ADU) if you'd left the gain at ~0.7 e-/ADU.

What about offset? Well, it's easy enough to figure out the minimum value a chip is going to produce and add enough offset in the ADC process to keep it such that this is never going to hit 0.

OK, so what should I set my gain and offset to?
The best value for your camera may not be the best value for other cameras. In particular, different makers set things up differently. For example, on a Meade DSI III that I recently tested, running the gain full-out at 100% let it just hit full well at 65,535 ADU. Running below 100% and it hit full-well at 40,000 or 30,000, or 10,000 ADU. There's no point in running this camera at anything less than 100% gain. On a CCD Labs Q8-HR I have, even at gains of 0 and 1 (on its 0-63 scale), the camera would hit 65535 on bright objects (like the ceiling above my desk). There's no point in running this camera at gains higher than 0 or 1.

Why is there no point? The camera only holds 25k e-. If a gain of 0 or 1 gets me to 0.38 e-/ADU (so that those 25k e- become 65535), running at 0.1 e-/ADU will only serve to limit my dynamic range. Each single electron already comes out to more than 2 ADU.

So, how do I set it? (man, you ramble a lot when you get going!)
1) Take a bias frame and look for the minimum value in it. Is it at least, say 100 and less than a thousand or a few thousand? If so, your offset is fine. If it's too low, boost the offset. If it's high, drop it. Repeat until you have a bias frame with an offset in, roughly 100 - 1000. Don't worry about precision here, it won't matter at all in the end. You now know your offset. Set it and forget it. Never change it.

2) Aim the camera at something bright or just put it on your desk with no lens or lenscap on and take a picture. Look at the max value in the image. Is it well below 65k? If so, boost the gain. Is it at 65k? If so drop the gain. Now, if you're on a real target (daylight ones are great for this) you can look at the histogram and see the bunching up at the top end as the camera is hitting full-well. Having that bunch-up roughly at 65,535 plus or minus a bit is where you want to be. If you pull up just shy, you'll get the "most out of your chip" but you'll also have non-linearity up there. You've got more of a chance of having odd color casts on saturated areas, for example, as a result. If you let that just clip off, you've lost a touch but what you've lost is very non-linear data anyway (all this assumes, BTW, an ABG chip which all of these cams in question are). Record that gain and set it and forget it. Never change it.

By doing this simple, daytime, two-step process you've set things up perfectly. You'll be sure to never hit the evil of zero and you'll be making your chip's dynamic range fit best into the 16-bits of your ADC. Again, all the cameras in question have full-well capacities below 65,535 so you are sure to have enough ADUs to fit every electron you record into its own intensity value.

Caveat
The above assumes you have more ADUs available than electrons. This is true as noted for the cameras in question here but isn't universally true. For example, if you have an 8-bit ADC, variable gain is quite important as you may want yourself to trade-off quantization error and dynamic range. You may be fine blowing out the core of a galaxy to get those faint arms and want to run at 1 or 2 e-/ADU instead of 10 or 50 or 200 e-/ADU. This happens in 12-bit DSLRs as well with their 4096 shades of intensity but not so much with 14-bit DSLRs and their 16,384 shades.

Please note that none of this has considered noise at all. The situation is even "worse" when we factor in the actual noise we have. If the noise in the frame is 8 ADU that means the bottom 3 bits are basically worthless. That 45,000:1 dynamic range is really 45,000:8 or 5,625:1 and you're not even able to really pull out every electron. But, that's a topic for another day. (Google "Shannon Information" if interested).

NEAIC and NEAF

NEAIC and NEAF 2008

I'm writing this on the plane, heading back from my first trip to NEAF and to NEAIC. Many of you may know about NEAF as it's the largest astronomical vendor show in the country. For two days, the town of Suffern, NY is invaded by more amateur astronomers than you knew existed. In fact, most of the amateur astronomers and vendors that you know exist show up at NEAF. I had a lot of fun catching up with people I met least year at MWAIC, meeting in person people I've known over the Internet for years, and making new friends. It's really an amazing event. You owe it to yourself to get here some year.

NEAIC is an imaging satellite conference that brings in phenomenal speakers and vendors dedicated to astrophotography. At NEAIC, I got to spend time talking with Al Nagler (whom I'd meat at MAIC last year, spending hours talking with about astronomy and audio gear) and David Nagler of Televue, Rui Trippa of Atik, John Cordiale of Adirondack, Tim Puckett of Apogee, Kevin Nelson of QSI, Alan Holmes of SBIG, the Bisque brothers of Software Bisque, Don Goldman of Astrodon filters, Bob Denny of DC-3 Dreams (and ASCOM-fame), and Al Degutis of Astrophoto Insight. Many others were there as well. NEAIC was run by Jim Burnell (AIP4WIN) and Bob Moore who did an amazing job getting speakers together and organizing things. There giving talks were some of the world's best imagers, sharing some of their techniques. Seeing folks like Ken Crawford, Neil Flemming, and Jay GaBany, whose work is simply stunning, present many of their techniques was a real education. Getting to spend some good time with them was also a lot of fun - all really great guys in addition to being incredible imagers. I know a number of the speakers are putting their talks up on their websites. Check out the links above to see what you missed. My modest contribution to the conference was a talk entitled "Guiding on the Cheap". I've placed a QuickTime movie of the talk up in the Tutorials section for people to watch.

NEAIC was setup to have talks than ran the full range, from beginner to expert. We had Dave Snay doing a session on what to do and expect in your first night of imaging, taking people through the gear needed and how to go about actually getting and starting to process your first shots. We also had a talk by Robert Reeves on what's new in webcam astrophotography. Talks then went all the way to the design of ultra-high-end optical systems tailored for monster CCDs by Peter Ceravolo and on building a 9" TMB folded APO by Dietmar Hager, with many in between. There were workshops on topics like using AIP4WIN by Richard Berry, CCDNavigator and CCDAutoPilot by Steve Walters and John Smith, and on getting the most out of Photoshop by Warren Keller. By having three talks going at once, NEAIC managed over 20 talks in two days. All in all, a lot learned and a lot of fun had. If you missed it, consider it next year or consider MAIC in Chicago in a few months.

All this, and NEAF hadn't even begun! While I grew up not far from Suffern, I moved away before the hobby really took hold as an adult, and I'd never managed to make it to NEAF. Well, I sense I'll be going back. If there is gear you want to see in person or people you want to talk to about gear, the gear and people can be found at NEAF. It's really impressive. You can find a list of vendors on the main NEAF page, but that may still not give you a real idea of what it's like. NEAF was kicked off for me at the Sky and Telescope party, which was followed by the OPT party. The number of people in the room there who have helped move our hobby to where we are now was amazing. The room was packed and the vast majority I certainly didn't get to talk to. But if you've not been to NEAF, I can give you an idea by letting you know who I got to really talk to. There was Dennis DiCicco of Sky and Telescope, Craig Weatherwax of OPT (we seem to share the same barber), Alan Traino (who runs NEAF and can sure tell a story), Doug George of Diffraction Limited, and John Smith of CCDWare. Of course, more time talking with the likes of Jim Burnell, Warren Keller, Al and David Nagler, Kevin Nelson, Ken Crawford, the Bisque Brothers, Al Degutis, and Bob Denney.

Then at NEAF, there was a mix of getting to see all the newly introduced stuff, getting to kick the tires on existing gear, and getting go scrounge around for nice bargains in the clearance bins. I went in wanting to meet the crew from Lunt Solar Systems and see what their new solar scopes were about. Sadly, things were cloudy and so I couldn't look through them, but I did get to spend some time with them on the table. Boy, they sure are tempting! Over in the Astronomics booth, I saw the 8" RC from Astro-Tech. 6", 8", 10", 12" and 16" scopes are in the works - real RCs at low prices. The 6" comes in at $1295 and the 8" at $2995. The 10" was something around $5k, I believe. In fact, there were a number of RC scopes, modified DK scopes, etc. there at lower prices than we've seen before by far. Mike Siniscalchi and I spent a lot of time talking with Mike Bieler of Astronomics about their plans and about Cloudy Nights. I also got to meet Russ and crew from Denkmeier and to hear about a really neat image-intensifier system they're working on and to chat with Ted Ishikawa from Hutech (another Borg may be in my future), and with Gary and Stuart Parkerson of Astronomy Technology Today.

Many of the above I'd expected to do while here. No, I didn't know about the RC scopes, but I'd assumed we'd have something new from Astro-Tech. I also assumed we'd have something new from Televue. That was their 8 mm Ethos. I got to get a look through a pair of those in a binoviewer. Holy cow! You could hardly tell you were looking through anything! But, most of this I'd expected to some extent. Exciting, sure, but expected in some way. What was also great to see was the new stuff from new companies (or at least those I'd never heard of). One that caught my eye was a slick polymer solution for cleaning optics. It's not inexpensive stuff, but it sure did so the job and I'll probably pick some up for the next time I'm trying to clean my CCD off. It bonds to the dust particles, solidifies, and you just peel it (and the dust) off. Very slick. Another was the StableMax from Telescope Stability Systems, a new company. While there are some great portable piers out there - some of which are just breathtakingly cool, these aren't inexpensive bits of gear. The StableMax was seriously sturdy and has a very trick setup for mating to the mount. A removable, indexed adapter plate attaches to your mount and then slides into a spot on the tripod. This makes it so you can change mount heads easily while using the same tripod (adapter plates range from $50-$100) - either if you have more than one mount or if you end up swapping mounts down the road. The machining was wonderfully precise and the thing wouldn't budge. I'm going to be taking some measurements of my EM-10 and talking to Tim Ray soon as this seems to be a great, well-engineered solution.

Add to this, I met a ton of users - far too many to list here (and far too taxing on my memory to recall all the names!) I'd like to thank all those that came up to say "Hi" and that they were big fans of PHD Guiding. Getting to talk with you and hear how much its helped and see how many people its helped is really wonderful.

If there's one thing to get out of this blog entry, it's not that Craig got to meet a bunch of folks. It's that NEAIC and NEAF let me meet a bunch of folks. If you were here, you could have asked Al Nagler about the new Ethos, Russ Lederman about the new coatings on his binoviewers, Gary and Stuart about what's coming up in ATT, etc. They're all here, they're all amateur astronomers like you, and they're all ready and willing to talk. You'll get to do that and you'll meet people you may have known in the ether for ages, but never actually met. You may come home a bit lighter in the wallet (others seem to have managed to spend nothing - Craig from OPT made sure that wasn't my fate within minutes of opening, selling me a Baader Hyperion zoom), but I doubt you'll mind. I can't imagine you wouldn't have a good time.

Wecome to Craig's Astro Blog

Welcome to my astrophotography blog. As the author of programs like PHD Guiding and Nebulosity, I get a lot of questions on user groups like the Stark Labs Yahoo group. While some of these cover things specific to the software, other things are more general. One goal of this blog is to bring together a number of questions and answers that come up often or are of broad appeal.

I also get a lot of cameras and other gear here for testing (see reviews in Astrophoto Insight and Astronomy Technology Today) and for integration into the software. A second goal of the blog is to give short-form reviews / thoughts on these.

This is my first blog. I have no idea how well this will work out, but it costs nothing but time to try. Hmmm, I seem to recall saying something like that when I started to write Nebulosity.

While starting things off, I'd like to give a big THANK YOU to Michael Garvin for helping me get this off the ground.

Craig