Starting out with a DSLR and a Newtonian

[EvanC]

Hi all,

I'm new here, but have a big question to start off...

I have a Canon EOS 350D digital SLR, and my dad and I are looking to get started with astrophotography using my camera and his 4.5" Netwonian.

There seem to be a few methods of doing this, but I'm unsure of which is the best for us, and what equipment we need (and, of course, where to buy it!). The scope has an EQ mount with a motor drive, but we've never used the drive.

I had a look around here, found some bits and pieces of information about what I'm looking to do, but wasn't sure so I figured I'd be better off to ask


Any help would be greatly appreciated.

Thanks
~ Evan C

[xelasnave]

Welcome to Iceinspace Evan.
Your question it almost how long is a piece of string.
You will need an illuminated reticle, which is an eye piece with illuminated cross hairs and read all in these forums about drift alignment. You need an adapter to fix the camera on the scope approx $35-00 from say Bintel or Andrews Communications.
Also you really need another scope to follow a guide star so as to keep the capture scope on target. Many people go for an 80mm scope for this purpose and often end up guiding with the large scope and capturing thru the 80mm scope. Have a look at the results in the Deep sky threads and you will see the fantastic results capturing thru an 80mm can bring.
You will need a remote control for your camera to activate the bulb feature as you can not simply hold it down manually during captures.
Try and find the celestial South pole and practice drift alignment and be prepared for a long initial learning experience. Astro photos demand a perfect alignment
Perhaps the best way to start is piggy back the camera and use the scope as a guide scope. With long exposures you can get delightful wide fields and learn the ropes in the process.
best wishes
alex

[Dennis]

Hi Evan

Before you invest too much money, it might be worth testing to see if you can achieve focus with the DSLR.

From what I understand (I have never owned/used a Newtonian), the prime focus image from the main mirror comes to a focus only a relatively short distance outside the main tube, where the focuser is positioned. This distance is usually sufficient for an eyepiece to intercept and magnify, but I have heard that some cameras will not come to focus on Newt’s. Basically, the focuser cannot be racked in far enough, so the camera ends up hitting the tube before the image comes to focus. This is termed “lack of back focus”.

If you were to make the diagonal (secondary mirror) larger to project the prime focus image further outside the tube, you introduce undesirable effects due to a larger secondary obstruction.

If you move the main (primary) mirror further up the main tube (i.e. towards the diagonal mirror) then this should cause the prime focus image to come to focus further outside the tube, but you may loose some of the light from the outer edges of the main mirror.

Cheers

Dennis

[xelasnave]

Dennis made a good observation. My focuser on the 150sn (reflector) has a tube extention that screws off to shorten it and on my 12 inch you can not reach focus ..not that I can use the camera on it as it is a dob mount. But if ever I decide to get it on the eq6 mount I will have to shorten the tube just a little or put on a lower profile focuser.I have thought of trying it on the eq6 like Mike but I have to add a guide scope which I think would just all be a little too much for it to work well for deep sky objects.
alex

[seeker372011 (Narayan)]

Given your current equipment perhaps you should consider to start with piggyback astro photography.

This means:
learning to polar align
learning to use your drive motors
learning how to process your raw images when you have acquired thes

You can produce some very respectable images , if you get these three factors right..but you may need to go to a dark site in order to do so

On the other hand when you have got this down pat, it will be a realtively easy step up to prime focus..by which time you will also start getting a feel for how much money you want to throw at this pastime

[iceman (Mike)]

Hi Evan, welcome to IIS!

What type of EQ mount does it have? Is it a light wobbly one, or a more heavy duty one?

You could start by just pointing the camera into the eyepiece and snapping away.. that'll work fine for the moon, and maybe for the bright planets. For deep space, you'll need to get it working in prime focus mode as others have said, or piggyback.

Don't worry about guiding until you get the basics right.

[xelasnave]

Originally Posted by iceman

Hi Evan, welcome to IIS!

What type of EQ mount does it have? Is it a light wobbly one, or a more heavy duty one?

You could start by just pointing the camera into the eyepiece and snapping away.. that'll work fine for the moon, and maybe for the bright planets. For deep space, you'll need to get it working in prime focus mode as others have said, or piggyback.

Don't worry about guiding until you get the basics right.

Evan that is good advice from Mike, you can have so much fun snapping the Moon just by holding the camera to the eye piece and snapping away...and marginal tracking will not prevent you..also you can get a feel of the software.. you may be able to take a few snaps and start working with a stacking program which not only a lot of fun you will get good results with the gear at you disposal now. Good luck. Try geting as good a pole as you can and try piggy back at increasing exposure times and you will see how important perfect alignment is because I suspect the stars will trail.. see if even without an illuminated reticle you can get it better and this will give you a feel for the considerations that come into play.
alex