Wide Field Mounting for Atik 314L+ with Camera Lens

[Gina]

Got the electric motor/gearbox focussing system set up for the 200mm f4 SMC Takumar on the 314L+. With a bright moon I decided to go for NB tonight with a clear sky forecast. So I set the Ha filter in position and set the exposure to 0.001s. Lined up and focused roughly on the moon. The exposure needed turning up to 0.003s for a nice image in Ha. Then slewed to a nearby bright star, upped the exposure to 0.02s and clicked on the star to enable FWHM and adjust the focus with the remote control. I got the value down from around 3 to around 1 with the star covering just 1 pixel. That seemed pretty good to me.

Then I slewed to M42 and centred it in the frame ready for some Ha subs. At that point the clouds came back! So much for the forecast! I got a couple of subs of 60s and a couple at 45s. There are holes in the cloud so I've left it running on 45s subs in the hope of getting something. It should give me an idea of how sharp the lens is having accurately focused it. When clear, 45s gives the trapezium stars at just under 65535. I don't know how much of the fainter stuff I shall get but it might give me a good Ha of the core. Next clear night I can set up for longer subs of ten or twenty minutes - ever the optimist

[Gina]

I made a little mistake in that I had the sequencer running and had it set for only 20 repeats so I only got 20 subs while I was in the house. I got another 20 or so and then set PHD going while taking 20s subs which were short enough not to be affected by PHDs calibration meanderings. The sky continued with bands of cloud and clear parts so I've continued taking subs. Firstly 2m and now it's running 5m subs. I don't think I dare go any higher with the cloud situation. A lot of the cloud is fairly thin and the guiding is working even with cloud cover though not quite as well as when there's a clear period. Every now and again guiding fails but only for a few seconds at a time and not enough to lose the guide star completely.

I've had the PHD graph up and guiding is a lot smoother with the new mounting arrangement - I was quite surprised. Mind you, I previously had the guide scope on top of the ED80 and it was probably rather flexibly mounted. Now everything is rock solid

[Astrokev]

Sounds like you have it sorted. Well done.

[RAC]

I really like the fov you get with the 314 and the 200mm lens.

[Gina]

Thanks The focussing works well, the lens looks good and yes, the FOV is great Conditions were dreadful last night with the cloud and processing the best of the data has not produced anything startling but does confirm that at least.

[Gina]

A single 120s sub and a stack of 18 45s subs

[Gina]

I've received the ali plate and timing belt to put the focus motor right underneath the lens but the temperary setup is working well so I think I'll leave well alone for now.

Here's a couple of photos of the mounting and focus motor drive.

[Gina]

Looking at my options for focal length I have 600, 510, 200, 135, 55 and 35 mm, there is a big gap between the 510 of the ED80 with 0.85x FR/FF and the 200mm lens. Two options occur to me. I have a Vivitar 300mm f5.6 telephoto lens and there's the ST80 which I use as a guide scope - 400mm f5. So that would give 600, 510, 400, 300, 200, 135. 55 and 35mm. I'm considering trying my 2x ED Barlow for the smaller DSOs though that doubles the FR giving 1200mm f15 for the ED80 (or 800mm f10 for the ST80) of course - but I've got lots to do before that and very little opportunity for imaging. I can use the ED80 as guide scope when using the ST80 for imaging.

[Gina]

Thanks Gina. I think the distance is 55mm so I would be interested to know if this is what you get.

I've found the EOS EF mount to sensor distance

Canon EOS bayonet 44

I'll measure the length of the Canon adapter then I can calculate the distance for the SW FR/FF to sensor for using the Atik kit.

[Gina]

A couple of hours of clear sky tonight and I've got 30 subs of 30s Ha and 6 subs of 600s so far and now I've set up 1200s = 20m subs but there are signs of clouds coming in so I don't know how many 20m subs I'll get.

[Astrokev]

I've received the ali plate and timing belt to put the focus motor right underneath the lens but the temperary setup is working well so I think I'll leave well alone for now.

Here's a couple of photos of the mounting and focus motor drive.

Gina,

How tight is the belt around the lens focus wheel? Since this is several cm's in front of the single mounting bracket, just wondering if this affects the alignment at all?

Regarding your focal length options, I personally don't think you need to fill in gaps in your range. 200 to 500 is not as big as it sounds in my experience.

[Gina]

Gina,

How tight is the belt around the lens focus wheel? Since this is several cm's in front of the single mounting bracket, just wondering if this affects the alignment at all?

It's not tight enough to affect the alignment very much - the image does move a little bit when I reverse the focussing direction. The belt heaving teeth and the focussing sleeve being ribbed there is a lot of friction plus the belt goes round more than 180 degrees so the drive from belt to lens is very good.

Regarding your focal length options, I personally don't think you need to fill in gaps in your range. 200 to 500 is not as big as it sounds in my experience.

I'll see ATM I haven't got the 510mm FL operational - I need to work out and adjust the spacing from FR/FF to sensor.

[Gina]

A bit OT... I measured SW FR/FF EOS adapter and it's just under 11mm so FR/FF to sensor distance is indeed 55mm - you were quite right Ian. I thought you would be

[Gina]

Ordered an 8mm and a 3mm T2 extension to give 11mm. I can get the other 0.5mm with a spacer.

[ianaiken]

Yes 55mm that's what I have finally. I ordered all kinds of adapters and got there :-). I also have a Geoptik Canon lens mount and with this I need to achieve 44mm backfocus for the EF Lenses - yet more adaptors!