Posts Made By: Alex McConahay

Generally speaking, you would be better off with a wide field refractor rather than an 8 inch SCT (which is what the ACF is, right?). It is hard to learn imaging on an SCT with its long focal length. It is even harder to get a wide field picture off on one.....They are not made for that. Also, since the ACF may not be the best choice, you might want to consider a German Equatorial Mount instead of the Fork. A GEM adapts better to a variety of tubes and is quite popular in imaging.

As for the vision problem, if you can read a computer screen you can do astroimaging. Won't be as easy as it might be otherwise, but you can do it.

The 40 D should do you quite well. You will also need a laptop.

Alex

Interesting question. I do not know the answer.

I would suppose if a club tried to join up as a "commercial Vendor" it would be acceptable. But that is just me, and I don't really know.

I just re-read the Terms of Service. I see nowhere that a member must be a "person" and certainly no mention of whether that person must be a human person or a legal person (such as a corporation). There is a requirement that the registrant be 18 years of age. Otherwise, I get nothing out of the TOS to answer the question.

In short, I would suggest you write Astromart itself to check on the answer. (Or perhaps Astromart LLC will be weighing in here sometime soon.)

Alex

I know many people who do. Some of them regularly contribute to scientific journals with data from their backyard observatories.

I am trying to get involved in that.

I think the chief tasks of amateur astronomers seems to be asteroid rotations, variable star timing, and occultations.

Check out the Society for Astronomical Sciences.

http://www.socastrosci.org/

Check out Buchheim "The Sky is Your Laboratory" book for more.

Alex

In the left column over there, you will see thre "Account Menu."

Click on it and look for "My Unused Ratings."

Take it from there.

Alex

Robert-- Let me clarify what you are saying....

>>>a Vixen NLVW 30mm eyepiece will not reach focus with the diagonal attached

This is a problem, I agree. I take it the focus tube is all the way in, and the eyepiece will still not focus. And I assume you are trying this at infinity. Did you notice if the end of the tube can be screwed off and allow you to attach the diagonal directly (without the two inch adapter)?

>>> the focal point appears to be almost exactly at the end of the extended drawtube.

I don't see this as a problem as long as when you put in the diagonal you can get the other eyepieces to focus--and from your next paragraph, it seems you can.

Before asking how much to cut off to make it ideal for imaging, you should probably remove the diagonal, put in the camera and all the things you plan to use with it (auxiliary focuser?? field flattener/corrector??, t-ring adapters, special diagonals for solar viewing, whatever) etc, and see if it will come to focus at infinity (not on a daytime object--make sure it is infinity.) Does it come to focus? Then don't cut anything off to make it good for imaging. As Jon pointed out, one does not use a diagonal for imaging (except for special purpose diagonals like Herschel wedges, Lunt, etc.). If it does not, then come on back and tell us what you have found out. I suspect it will come to focus if you have determined the focus is just past the end of the extended tube. (Cameras typically need 30-60 mm in from the front of the camera to the imaging plane.)

If you still want to cut off some to make your NLVW work, then it is up to you to decide how much.

You do want to keep the focuser tube as short (in extension from the main tube) as possible for imaging. The less you have hanging off back there the better.

Alex

Have you taken the subject up with Scotty? He is about the nicest person in the world, and would not want one of his scopes to be less than satisfactory.

Maybe he knows the problem and how to fix.

Alex

This particular moderator has seen this particular problem many times, and can think of nothing to do (that has not already been tried a million times) other than to appeal directly to the powers that be:

mailto:[email protected]

Give that a try.

Alex

>>>>>what is the typical method for taking/making a dark frame?

After an evening of imaging, take a series of exposures with the same ISO and shutter time as the light frame exposures you just took. THe only difference is that you have to put the cover on the scope so that no light reaches the sensor. (Alternatively, you can remove the camera from the scope and put a cover over the sensor with a body cap or a capped camera lens. You should also block off the camera viewfinder so no light leaks back in from there.) You take them the same evening so that they are at the same ambient temperature as the light frames.

>>>>>>I gather that you take a blank, dark, shot to minus the noise that is inherent in the image.
Yes. The concept is that there is a certain amount of noise due to heat in the camera. This noise forms a pattern based on the hotspots on the imaging sensor (say, near an internal camera power amplifier or something). If you know the pattern of this noise, you can subtract it from the good signal that comes from the celestial object.

>>>>> However, doesn't the camera do that automatically,
Yes, if you have "Noise Reduction" set in your camera. No if you do not.

If you have set the "Noise reduction" function in your camera, the camera takes the regular light frame and immediately takes a dark frame, subtracting the dark from the light. THis is all very good. However, that means that it takes ten minutes to take a five minute exposure. (Five for light frame, five for dark.) THis cuts down the number of light frames you can get to half. Most of us would rather use time under a dark sky to take light frames. So, we prefer to take the darks at the end of the session while we are packing up or going off to take a nap.

>>>and why does one need so many?

In addition to fairly fixed noise, the camera has random noise (gamma rays, quantum fluctuations, whatever.) Taking multiple darks (and same applies to lights) lets you remove these weirdnesses by averaging and other algorithms.


>>>>>From what I understand, the D60 takes as long to process the image as it took to take it, b/c it's doing the dark frames automatically
Again, it takes "automatic darks" only only if you have Noise Reduction set, and see the earlier explanation. YOu can see that it takes as long to take a dark as it does to take a light (as you said.....) but to take the whole exposure (light plus dark) takes TWICE as long.


>>>>>what software do you like to use for these images?

There are a number of candidates for the software. I uses Images Plus, but others use Nebulosity and a number of other packages.

Alex

C'mon, give him a break....The guy is a plastic surgeon.

I mean, you realize that there are some people out there think the guy who really needs to get a life is the astroimager out there spending ten thousand dollars on equipment to take the ten millionth picture of M42......Or the guy reveling in excitement after finding NGC 9096--the thing you can't even see in the eyepiece except for a discoloration in your floaters?

Alex

Wjhat a pretty star!

Alex