DSLRs and Astrophotography (Newbie here)

Vince · Post by **Vince** » Wed Jan 07, 2004 7:52 pm

Hi,

I'm pretty new to astro-photography but always had and interest in it. With recent developments on Digital SLRs, I've finally got the opportunity to try it out.

I'm currently using a Celestron C90 Maksutov-Cassergrain telescope but somehow, when I tried to photograph stellar trails, I get lots of hot pixels. Is there any way of removing them on camera? (other than post processing with PS).

Also, do you guys have any opinions on the Celestron Nexstar 130GT Newtonian? Is it any good for Astrophotography?

Thanks in Advance

Post by **weixing** » Wed Jan 07, 2004 8:20 pm

Hi,
To reduce noise(hot pixel), you should turn on your camera Noise Reduction. Also, you can reduce the noise via post processing. This is done by taking a dark frame with the same exposure of your stellar trails. For example, if your exposure of the stellar trails is 60s, you should also take a dark frame for 60s. Dark frame is taken by covering your camera lens, so that only the noise is capture. Then you can use software to reduce the noise from the stellar trails image.

Anyway, how long is your exposure?? Unless your site and the sky is dark, long exposure will also capture the light-pollution on the image. Also, don't worry if there are a lots of noise, noise is something that every digital camera will have when doing long exposure at high ISO setting.

Happy imaging and hope the information is useful.

Vince · Post by **Vince** » Wed Jan 07, 2004 8:38 pm

I've tried taking stellar trails off my 10D with exposure of about 10 minutes. Ended up with a LOT of extra "stars"

a little disheartening.

Low ISO shots (between 100-400) as I am aware of noise problems with higher ISOs.

It was shot using a 50mm lens @ f/22 unguided (for star trails)

Vince · Post by **Vince** » Wed Jan 07, 2004 9:07 pm

This is my first attempt at photographing Saturn using the C90 with T-Adapter n T-Ring and Canon's EOS 10D. I find that I can "see" Saturn more clearly n sharper through the 9mm eyepiece but for some reason it becomes fuzzy n indistinct when hooked up to my 10D...could be a focusing problem though coz it's really hard to focus when my viewfinder is 1) dark n 2) small.

Post by **weixing** » Wed Jan 07, 2004 9:08 pm

Hi,
OK, noise in digital camera are something you have to get use to it when taking long exposure shot.

You can try the method that I mention to reduce the noise. By the way, heat will also generate extra noise, so turn off the LCD before the shot. Also, set the camera to do no image manipulation or enhancement and turn off any sharpening, contrast, or brightness settings - this also enhance the noise. Remember to turn on the noise reduction and applied the same setting for the dark frame shot.

Astrophotography is something that require a lots of patient and since you got such a good digital camera, don't waste it. Next time, I will try it on my CoolPix 4500, but my maxmium exposure is only 5 minutes... I really envy you

Anyway, what I think is that the "noise" may not be 100% noise, but the light pollution... So, next time try again at a darker site. Also, the image may be look ugly when you see it at actual size, but it will look a lots nicer when you scale down to 4R.

Happy imaging and have a nice day.

Post by **weixing** » Wed Jan 07, 2004 9:21 pm

Hi,
Using the LCD to focus is difficult, so it is very normal that your first attempt is out of focus. Since the moon is out, focus on the moon first before you point at saturn. It should be quite easy to focus on the moon. Take a shot and zoom in the image to check focusing. Then take a dozen shot and use RegiStax to stack them to get a better image.

Have a nice day.

Vince · Post by **Vince** » Wed Jan 07, 2004 9:26 pm

Hi WeiXing,

Thanks for the advice. Will try it out and if the results are good, will post here with thanks to you

Btw, any idea if there are 3rd party piggyback attachments available for Celestron's Nexstar 130GT? They don't seem to produce any of their own.

Sorry if I'm a little long-winded. I'm having trouble with the supplied motordrive for the C90 (seems to be a little off) either that, or my polar alignment really sucks!

Post by **weixing** » Wed Jan 07, 2004 9:52 pm

Hi,
What is your scope tube diameter?? I think some of SingAstro member should know where to get one.

Yes, you need to do a proper polar alignment and carefully balance your scope. Remember to balance your scope with your camera on. Also, all motor drive will have some error. If you want to do long expourse, you need to do some guiding.

Have a nice day.

Post by **VinSnr** » Thu Jan 08, 2004 11:19 am

Vince wrote:I've tried taking stellar trails off my 10D with exposure of about 10 minutes. Ended up with a LOT of extra "stars" a little disheartening.

Low ISO shots (between 100-400) as I am aware of noise problems with higher ISOs.

It was shot using a 50mm lens @ f/22 unguided (for star trails)

Dun use that 10D for star trails...you are wasting that 10D only...

That 10D can take a lot of far better astrophotography shots. Most important thing is get something you can track. And for 10D, you can't even focus using the LCD screen, so you need to use something else.

I bought the Stellar technologies Stilleto focuser and that thing works like a charm on the 10D.

Get a good mount first.

blurblock · Post by **blurblock** » Fri Jan 09, 2004 12:37 am

Vince wrote:I've tried taking stellar trails off my 10D with exposure of about 10 minutes. Ended up with a LOT of extra "stars" a little disheartening.

Low ISO shots (between 100-400) as I am aware of noise problems with higher ISOs.

It was shot using a 50mm lens @ f/22 unguided (for star trails)

Hmmmm .... maybe I should try to take star trail again ... this time with 10D

.... ok .... wait for the moon to hide itself ......