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Just got a TS OAG

Catanonia

By Catanonia
in Imaging - Discussion

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Catanonia

Catanonia

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I used to have a Lumicron OAG and worked brilliant. But is was too big for the MN190 scope I have for the back focus.

I have just fitted to my QHY9 and filter wheel and looks like it is going to work with space spare :smiley:

Hopefully will be able to reduce a lot of weight and hence guiding issues associated to that by removing the other scope and adm dual bar.

Fingers crossed

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fatwoul

fatwoul

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Good luck, Cat. I really hope it works for you, as it does seem to completely eliminate flexure issues.

I have the Atik OAG on my MN190, and at the moment I'm having the same troubles that blinky describes. In my case there might be a solution to it, but time will tell.

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SteveA

SteveA

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I've also just bought one of the TS OAG's..

I've managed to achieve focus on my main imaging camera (Atik 314l+) and the guide camera (QHY5) by targeting a tree in the distance..during daylight. I struggled at first..just couldn't get the QHY5 to see anything, the problem was the images being over exposed even using the shortest exposure on the camera (initialy I though this was a focus issue!). In the end I restricted the aperture on the telescope and then started to get a good image through the OAG.

I've still to try the setup at night however!.....just keeping my fingers crossed I'll find a star through the thing!

Steve

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fatwoul

fatwoul

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That does seem to be the biggest issue with OAGs, Steve, and certainly my experience so far.

My hunch, at this early stage, is that my OAG might serve me better if/when I get around to a larger CCD. With the 314, I don't have much space to play with, so if a guide star doesn't appear for an object, I can't move around much to find one.

Oh well. I'll just have to buy an Atik 4000 afterall. :smiley:

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Catanonia

Catanonia

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Update.

Well initial testing for 10 mins on Vega during the short time the clouds were away shows that at least I can get focus with the QHY9 and filter wheel with the TS OAG in place.

Couldn't focus or find any guide stars, but didn't put much effort in to this part.

Just glad I can focus the QHY9 with everything in place.

So 50% of the way there, the TS OAG will work in terms of back focus, which is why I sold the Lumicro OAG.

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Catanonia

Catanonia

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Congrats you have the "easy" bit sorted....

now the fun begins... I have a handful of Solder tipped grub screws left drop me a pm if you want a couple... once you have chewed up the slot in the prism arm your on a hiding to nothing...

Peter...

Thanks mate, you have a PM :smiley:

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NickK

NickK

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I found the OAG focusing quite simple.

Focus the main scope using a flux density application (ie any focuser that shows the sharpness in a graph). Once that's focused then focus the OAG guide scope doing the same.

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Komet

Komet

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Sounds like an advert for SX but ...

I use an SX filter wheel with the SX OAG and Lodestar. My CCD is a QHY IMG2Pro (like a 314L but quieter thermally).

I get a full field of guide stars from the Lodestar and focusing took about 5 minutes. Don't need to move it any more now - swapping it from my 190MN to my ZS66 presented no problems at all. Focus the main camera and the Lodestar is all ready to go. The OAG has been possibly the best bit of kit I have ever bought. No flexure any more so no drift which is nice!

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Catanonia

Catanonia

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Ok a step closer to getting this to work.

I just couldn't get focus on the Guide Cam on the TS OAG.

I had the QHY9 focused, but nothing I did would get the QHY5 guide focused until I hit a brain wave.

Measure the focus point of the QHY9 and then re-focus with the focuser on the tube until the guide hit focus. This would give me the difference or how far out I was.

It seems quite a bit since I have the OAG on the tube side of the filter wheel. About an inch or maybe less difference. For the 1st time I actually saw stars on the guide OAG.

So looks like I need to get some T2 extenders to pull out the guide camera to achieve focus.

Is my logic right.

QHY9 focus at poistion A on the drawtube.

QHY5 OAG guide focused about 1 inch further back on the draw tube at position B

Therefore I need to put an extended on the QHY5 guide of B - A mm to push the guide camera further away from the prism.

I think I got the logic correct.

Anyway, order a T2 extension set from FLO, will come in handy with all the bits I have now.

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Psychobilly

Psychobilly

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I used a T-rotator that I got from Bern.. added the extra few mm and makes aligning the guide cam with RA/DEC a doddle.. I Picked up a load of t extensions from Astroboot and machined them to different lengths...

Some peopel find the helical focusers quite handy...

Take a look at the options on the TS site...Bern can get them pretty quickly if he doesn't have them in stock...

Again get it close in daylight first...

Peter...

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Catanonia

Catanonia

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woohoo,

Got it working. The focus is very fine on the guide OAG

Done some testing tonight and managed 15m and 20m subs in Ha with perfectly round stars :)

Now to strip mount and remove the old ED80 guide scope and re balance / align and go for some proper length targets

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Catanonia

Catanonia

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Mount all stripped and MN190 mounted centrally and perfectly balanced in all 3 axis with all the kit on. No more ADM and guide scope for me. Hopefully tracking will be bang on with about 15 kg of weight missing from the counterweights and addition scope + accessories.

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Catanonia

Catanonia

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The QHY9 + filter wheel + adapters + TSOAG is 60mm from QHY9 face to MN190 focuser face.

The QHY9 + Filter + Adpaters + TSOAG = 40mm leaving 20mm backfocus

The OAG prism face to focuser face is 20mm as above the backfocus

I added a 4mm T extender to the QHY5 to give me more play as without it, the QHY was on the very edge of the prism column. Adding the 4mm T extender gave me more wiggle room.

My prism is just in the 2inch FOV.

My TS OAG is infront of the filter wheel on purpose to help find stars without fiter interaction.

Obviously depend on how far in you push the prism into the optics view, but gives you an indication.

If you aer going to get a TS OAG, I would recommend at least buying a couple of 4mm T Extenders.

No way could I test during daylight as the cameras are too sensitve and just whited out even on min exposures. Well the QHY9 CCD did anyway.

I spend about 3 hours last night on Vega finding the focus point on the OAG and then calculating the focus addition, removal for the main CCD with spacers. The problem I initially had was that the focus point for matching it all was on the very edge of the prism arm and hence my problems.

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markcol

markcol

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Great stuff Cat. You're well away now, helpful tips too.

(Pity the TSOAG doesn't come with a couple of short T extension tubes, would make life easier for most peole setting up for the first time).

Peter's Baader T rotator looks very handy though.

Mark

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  • 2 months later...
Atacamallama

Atacamallama

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I've also just bought one of the TS OAG's..

I've managed to achieve focus on my main imaging camera (Atik 314l+) and the guide camera (QHY5) by targeting a tree in the distance..during daylight. I struggled at first..just couldn't get the QHY5 to see anything, the problem was the images being over exposed even using the shortest exposure on the camera (initialy I though this was a focus issue!). In the end I restricted the aperture on the telescope and then started to get a good image through the OAG.

I've still to try the setup at night however!.....just keeping my fingers crossed I'll find a star through the thing!

Steve

Thanks for that type about restricting the aperture... I had got stuck at that point ....

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