Help with taking astro photos

newhobby · #1 05-04-2006, 12:38 PM

I have a 10" LX200GPS and have been doing casual obserbving for about 3 years. I have been going to the SPSP for 3 years and have been progressively getting interested in astro photos. I now have a canon EOS 350D and DSLR focus (bought last week). I am reading through the manual but I guess I need an overview as I am getting bogged down in detail.
Basically do I connect the camera to the scope and laptop ( as well as the guiding cable), look at a not too bright star, take a photo, analyse the shot and adjust focus till ok, lock my mirror lock on the scope, slew to the object I want to photograph, then take the photo (using either gut feeling or the calculator DSLR has on board).
I understand when I take photos for too long I will get trailing but then I will have to buy a wedge.
Is this the theory? I know it's a dumb question but I am very new to this.

JohnG (John) · #2 05-04-2006, 01:13 PM

Firstly, there is no such thing as a dumb question.

The usual sequence is, attach the camera to the telescope vide a T-Ring with the appropriate Canon EOS adapter. Now, this next step is dependant on whether you have the appropriate cables or not, for the moment use the USB download cable that came with the camera, plug it in and also plug it into the Laptop. Your Laptop should pick it up immediately and a download screen will appear, click out of that and start DSLRFocus, connect the camera in DSLRFocus and go to focus mode, there is a default screen of 4 seconds exposure and 800 ISO, click your spacebar to take a photo, on the downloaded photo, move it around until you get a not to bright star, click on it then either rack your focus in or out until you get the highest value, on your scope, lock the mirror AND double check the focus again incase of slight mirror movement. Then go to the expose mode. I would go to the object you want first, then focus, with an SCT you have the problem of mirror flop, better to focus on a star near the object.

Bear in mind that you will be limited to 30 second exposures with the USB cable. You will definately get trailing without a wedge and it will happen quickly at f/10, 2500 mm focal length.

For long exposures you need to get another cable.

Hope this helps a little.

JohnG

[1ponders] (Paul) · #3 05-04-2006, 02:14 PM

Ditto to everything John has said. Plus a couple of other things to think about as well as the wedge.

1. to connect the camera t ring to the visual back of the SCT you will need a T thread adapter as the SCT doesn't have a T thread
2. Do you have the meade Zeroshift microfocuser with your GPS? If not consider getting one. It makes focusing much much easier
3 get a piggy back bracket and a freely rotating head like this for some wide field work.

As John has said at 2500 mm focal length you are going to get field rotation fairly quickly. If you go piggyback for a while with only short focal lengths (50 - 100mm for example) you may be able to get up to a minute without rotation not using a wedge. It also depends on where you are aiming in the sky as well as the focal length.

JohnG (John) · #4 05-04-2006, 02:38 PM

There was one thing I forgot to mention, make sure you go to Setup Menu 2 on your camera, go down to Communication and change it to PC, otherwise it will not talk to DSLRFocus.

JohnG

newhobby · #5 05-04-2006, 02:45 PM

Hi Guys
Thanks for that - I will experiment - I have the t-ring etc. I focus using the motorised microfocuser on the scope dont I - there's nothing in DSLR focus I need to do with focusing. Do I also leave the ISO on 800 for astro? ...sorry to be a pain.

JohnG (John) · #6 05-04-2006, 02:54 PM

DSLRFocus has a focus control inbuilt, as far as I am aware you require ASCOM for it, I focus manually with a 10:1 focuser, once you are close you only need very fine movement, I don't know if the Meade focuser is capable of that. As far as the ISO setting is concerned, basically, anything goes although I tend to use 400 to 800, just experiment, you will have to do quick shots so 1600 would probably work for you.

Your not a pain, it can be a steep learning curve.

JohnG

[1ponders] (Paul) · #7 05-04-2006, 03:06 PM

The meade focuser can be used, for autofocusing and manual focusing through DSLR Focus though the backlash in the Meade focuser can be a bit of a problem at times. From memory it should work through your normal laptop to telescope serial connection. And yes you will probably need to download the latest ascom for it to function properly though if you have kept your Autosuite up to dates you may find the you are already right to go.