Jm1973

Hi Budgie, thanks for the detailed reply. That sounds like it could do the trick. I will try it tomorrow assuming the clear weather persists. Many thanks.

Thinking about it, if I'm screwing in the front part of the finderscope then that should mean I am shortening the focal length. So I think that means I need more inward travel. Does this mean I'm looking at cutting down the finderscope tube?

Hi. I've been imaging for about 5 months or so now, and getting along ok unguided so far. I can get 3 minutes subs without too much hassle. However, quite often I have a lot of what seems to be 'walking' noise. I have bought a GPCAM2 and adaptor and had planned to use it with my Skywatcher 9x50 finderscope to autoguide, partly so I can dither and partly to have the chance of longer exposures. However, I have been unable to get it to focus. I can get a bright star in view, but it is very large and diffuse. I can bring it towards focus to a point by screwing the two front parts of the finderscope clockwise, but when they are tightened as far as they can go inwards, the star is still very much out of focus - by what seems to be quite a long way. I am still a bit clueless about focusing. Does this mean I need more backwards travel, ie. an extender or spacer of some kind, or do I need to look into cutting down the finderscope tube? Or something else? If anyone has come across this before and has any helpful suggestions, I would be very grateful.

So I've been doing a bit of research and I think I've found out what's going on... Firstly it's not just that the focal point is quite far forward, meaning that the addition of the rotator effectively stops me from being able to achieve focus. Also there is a lot of coma and other distortion, which there shouldn't be as I am using the dedicated 0.85 reducer. I have discovered that the sensor of the camera should be 55mm back from the reducer. I measured and mine is something like 100mm back. When I bought this it came with an adaptor which connected the reducer to my Canon 450D. However, it is not the M48 to EOS adaptor that is sold by FLO, it is one of these: Obviously this adds way too much backward spacing for the reducer to work, and also pushes the camera further back meaning it has to come further forward to achieve focus, if I am correct. This would seem to be the source of both my issues - focus and field distortion. I am going to purchase the Astro Essentials M48 to Canon EOs adaptor and see if that sorts things out. Sadly I sold the rotator when I thought I couldn;t use it, and will probably have to buy another one now. Ah well.

Great. That sounds like it will do the trick. /puts hacksaw away

Thanks. Thought I was going mad for a minute then.

I'm focusing on the roof of a building about half a mile away. I thought it was the other way around though? ie. it's further in when focusing to infinity. I am probably wrong.

Aha! This looks interesting. So this fits in place of the stock connector on the 0.85 reducer? And enables rotation?

Hi everyone. I need to ask for some advice. I recently bought an Evostar 80ED DS Pro, with the x0.85 dedicated flattener/reducer. It is fitted with a Moonlite CF focuser and Moonlite stepper motor. I haven't had chance to use it yet due to weather, but I have taken it into the garden during the day and tested focus with ny DSLR attached, and I can achieve focus at about 2300 steps out from 0. So far so good. However I also just bought one of the dedicated Evostar 80ED rotators from FLO. I fitted it and tested again during the day, and now I cannot get enough inward travel on the focuser to achieve focus. Do I have any options to enable me to get focus with the rotator? I don't really want to be cutting down the OTA or anything. Or do I have any other options for rotating the DSLR? I suppose I could turn the OTA in the tube rings to assist in framing, but I was hoping for something more accurate and less of a faff. If anyone had any experience with this, or any ideas generally I would be very grateful.

They are currently in stock at widescreen centre.

Great. I'll take a look.

To be honest I haven't even tried tightening the screws yet. It may be that that would be enough. Thanks.

Yeah, it defintely needs locking. I attach a DSLR and if I don;t lock it goes out of focus during the session. I think it might be a consistent thing. I need to run some tests when I'm not imaging and so not under pressure. Thanks.

Maybe the OTA is put on slightly differently and the weight distribution affects the PA slightly?

That sounds like good advice. Thank you.