AP help!

[Steve1976]

Need some help from all you expert astrophotographers out there -

Finally got a chance to set up the gear for prime focus using my canon 550D on Skymax-127. All the parts fit up nicely (camera without lens, canon t-ring, and t-adapter) into the back of the scope. Everything polar aligned (sort of, well to a newbie standard!).

I point at something interesting and turn the camera on live view. Nothing. I can get no picture, just black. Turned the focus on the scope slowly from one end to the next, still nothing.

Any thoughts? I'm hoping the scope is compatible for Prime focus AP? Or is my problem something do to with the central obstruction? I tried this both with and without the t-adaptor. Do I need a focal reducer or extra part?

I'm attaching the various parts I use (excluding camera without lens)

[Horus]

Hi Steve one very important thing , did you take the lens cover of the scope ? This happened to a friend of mine once. Sorry I know its a daft answer but had to ask.

[Steve1976]

yeah mate, it was the first thing I checked. I shone my red torch over the front of the scope and the live view screen recorded the red light.

[Pete Presland]

can you see anything in the day if you try it?

[valleyman]

What was you trying to focus on?

You will not see any nebula, or galaxies on live view, only very bright stars.

You need to focus on something like Sirius first, then align onto the subject and click away it takes time for the camera to absorb the light from DSO's which is why you set the Camera to BULB and open the shutter for long exposer

You may be getting to much focal lenght with the barlow, if you unscrew the 1.25 EP holder and then screw the T Ring in its place and attach the camera that way, you may achieve better focus.

[Steve1976]

Thanks for the reply guys

Bunnygod1 - not actually tried that will definitely try it day time

Valleyman (Pat) - yeah I went for Betelgeuse. I also tried just hooking up the camera and t-ring without the barlow/adaptor. Still nothing. I even took some shots. Just pure black. 'Tis very strange.

But my set up looks ok? I mean I am hooking the bits up ok?

[GrantEb]

When trying to focus, first look through the viewfinder, with liveview off, on a bright subject.

When switching on liveview, use highest ISO, and longest exposure.

But first get an idea of focus position on a distant subject in daytime.

HTH

[Steve1976]

thanks GrantEB. That's basically what I've been doing, but definitely need to try daytime.

it isn't the central obstruction in a MAK then? or anything to do with me having to buy some kind of focal reducer?

[roebuck]

I had this problem with my 200pds. It turned out to be the extension tube that I use on my sw 80 to be too long. I then used a shorter T adapter and focused instantly.

[Cornelius Varley]

Focussing the Mak with a camera attached shouldn't be a problem. With a barlow attached, however, the FOV will be quite small, so you won't need it. Take a look at this FOV calculator to see a representation of the field of view of the Skymax127 with the camera attached.

Peter

[Steve1976]

i don't think I've been using a barlow to be honest unless the t-adaptor is a barlow? But it sounds like I'm better to attach the camera using only the t-ring and not the adaptor to reduce the focal length?

[jgs001]

You should be able to reach focus without issue. There's a lot of movement in the Mak mirror to enable that to happen. The 127 at f/11 is quite slow for deep sky targets, it'll work on the brighter ones, but you'll need longer exposures, and push the other settings. I'm not sure on the exact amount, but I did check out the difference between my two scopes... To get the equivalent of a 1 minute exposure at f/7.5 on my refractor, I need to use 90s on my f/9 RC, so it would be probably nearer 115s on the Mak. You'd probably be good on bright targets like the globular clusters, but you'll need longer exposures.

Oh, you shouldn't need the T adapter, the rear of the fittings on the Mak I believe are threaded for a T ring already.

[Steve1976]

thats great news John thanks. I was beginning to worry that Pfocus would be an issue with the MAK. Looks like human error then! I will give it another go with just the t-ring.

[jgs001]

I've done just that, Canon 450d, T-Ring direct to the rear of the Mak and imaged the moon, and a glob or two with my Skymax102.