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OTA Woes and Money being sucked up quicker than a blackhole


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Hi all,

I'm having some OTA woes which has left me at a cross roads. Irecently spent a lot of money buying a QHY9 CCD, buying 2" filters etc only to find that i cant get my QHY9 to come to focus with my 8" skywatcher Explora 200P OTA.

Now it looks like i might have to change the ota which would be a shame as i have the skywatcher motorized focuser using shoe string FCUSB unit.

I'm starting to feel like it's an expensive uphill struggle that seems never ending, and i'm not sure of my options and need the advice of fellow astrobods...

Option 1

======

Buy a replacement ota, something like the 200P DS and loose motorized focus control.

(Is anyone using a QHY9 with the new 200P DS OTA ?? I know they moved the mirror, to help ccd come to focus easier, I just dont want to buy another OTA and find it doesn't work either)

Option 2

=======

Keep the current standard 200P tube and buy a motorized moonlite in the hope that i get enought travel from the low profile of the moonlite.

Otion 3

======

Scrap the newtonian all-together and maybe consider saving for a 100mm refractor, something like the newskywatcher pro series, where I should have no problem achieving focus.

would a good 100mm refractor like the skywatcher pro give better views of the planets than the 200mm 200P DS ??

Thanks,

Rich.

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Hi Ken,

I wouldn't have the first clue of where to start moving the mirror. I dont actually know what's involved, but i'm scared of messing it up, whilst if i sold the current OTA, i could get some money back to put towards the the next new OTA.

Rich.

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I hate to sound like a git but have you considered whatever you buy may have problems somewhere down the line and sooner or later you will have to get stuck in and do this kind of stuff.

Very little in the world of astronomy seems to work out the box (beleive me I have been there). If you went the Moonlite route you may well find the challenges of getting that installed may be too much. Chances are you wiull have to widen the tube holes, maybe even take the spider and the secondary mirror out and recollimate from scratch - if your anywhere around near Gatwick I'd be happy to try and get you going by moving the mirror and showing you whats involved but I suspect sooner or later you will have to take on these kinds of things.

I know that may come across as harsh but I'd hate for you to sell the scope, blow some more cash and then maybe find you need to make other mods which are also beyond you.

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I can understand the fear believe me - but realistically whatver you buy sooner or later your going to have to either collimate it, tune it, make mods in some way shape or form.

Unless you go for a referctor your always going to need to collimate. Moving the mirror up the tube really inst very hard - it really comes down to being able to recollimate the scope.

Perhaps one of the other imagers whos using the same sort of kut could advise better. Steppenwold uses an 8" and a 10" Sky-Watcher as far as I know - maybe he could advise on this score.

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I don't know how you've tested the problem as you don't write much about that. So at the risk of coming off sounding like a git have you tried narrowing down what piece of equipment is actually causing the trouble?

For example, try using the ccd on the telescope without the auto-focuser on the telescope. If you can manually achieve focus then it's a problem with the auto-focuser. If you can't manually achieve focus then you're looking at mirror location or issues with the ccd itself.

Have you gone to the QHYCCD forum to see if others are having similar issues? There could be some hack you can perform to get it working with your telescope found there. qhyccd.com - Index

I guess what I'm trying to say is that before you choose one of your listed options you should try to narrow down what your problem really is. It could end up saving you money.

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Hi all,

The auto focuser is not the problem, i'm tried manually focusing and can't get anywhere remotely close. I have moved my filter wheel outof the optical chain so it's simply the ccd directly going into to 2" adapter on the draw tube.

With regards to collomation, I have no problems collimating my scope. A few people have mentioned moving the mirror further up the ota andthat it's not hard. What is involved in this process ? where can i find any links for this ?

Rich.

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Rich,

I'm not familiar with your scope. The main mirror support cell is usually held in the tube with three screws. The idea is to determine how much additional focus you think you need... say 50mm.... and then drill three new holes in the OTA 50mm in front of the original holes and remount the mirror cell. That's basically it.

Ken

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I remember on my Skywatcher 10" newt that the cast mirror cell could not be moved up the tube as it had a flange which butted up against the end of the tube, hence the tube would have had to be cut, which complicates things a bit. Not sure what this particular one is like though.

ps, astronomy has sucked up more of my money than I care to think about, with swapping and changing equipment. It seems to be the way of things, particularly with imaging.

Edited by sgazer
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I do feel for you Sir ! But this is the Game were in. Changing gear frequently on the imaging side of things & just bought my 1st proper astro ccd camera w/ filter wheel. I changed the Stock focuser on the 200PDS to a Moonlite only due to not facing problems like yours (if I might have any in the future), I have yet to have my 1st light with my Atik 16ic, but I don't envisage having any problems with focus on the Moonlight (thats what he says !)

After spending a good deal of money, which I will not say how much :headbang: & wish not to continue to do so, I have arrived at the crossroads, if there is such a thing in imaging. I have rationalised my gear after experimenting with various ota's, my imaging scopes are going to be my 200PDS, 80mm ED Refractor with a 80mm Guidescope. Cameras: Image with my 450D & the Atik also get a cheap s/h guide camera.

Sorry to ramble, but there is another alternative, get out of imaging & stick to observing, way hell of a lot cheaper. Many thoughts do cross my mind about this, as you say it's a massive blackhole where our hard earned cash is going & something I might consider.

Just some thoughts.

Cheers

Nadeem.

Edited by Deneb
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Hi Ribuck

I'm not an imager but I have seen several guys wrestle with these issues.

A large Newt is one of the hardest scope to get working well with an imaging setup.

I would consider a shortish refractor as the scope to 'learn the ropes' and once this is done then you can move up to the larger scope.

Cheers

Ian

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The mirror on the 200P Explorer sits in a big metal flange that then goes on the end of the tube like an end cap held with 6 screws. I don't see how you can move the mirror up the tube without cutting the tube.

post-17592-133877431496_thumb.jpg

post-17592-133877431504_thumb.jpg

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Work out how further up the tube you will need it to be, say for example 40mm then slot the tube between 30 and 50mm this will give you a range of 20mm to achieve perfect focus.

EDIT

by looking at your picture Glider your cell has a ridge running around it that the tube sits on so my idea might be impractical for this.

Edited by Doc
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If I visualise it you put the 2" nose piece on your camera straight into the 2" EP holder on the focuser and can't get enough in focus. How long is the EP holder, could you cut the length of the 2" EP holder down and gain 20 or 30mm that way?

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I do think you need to try and dertermine how much more in-focus you need before all the good advice offered so far can be realistic. From the photos it seems that slotting or repositioning of the attachment srew holes is not an option. Replacing the mirror cell adjusting and locking screws with appropriately longer ones could do the trick. Shortening the tube is easier than you might think provided that you have a suitable hacksaw and used to using one. Remove the mirror cell complete with mirror, wrap a length of suitably wide masking tape round the bottom of the tube and cut using the upper edge as a guide. File off the sharp edges, re-drill the attachment holes and refit the cell. Shouldn't take more than an hour.

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I was just about to type that as well Peter.

The cheap option, as long as you have a drill and hacksaw and it won't cost nothing is to cut the bottom of your tube off.

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Thanks everyone, and thanks glider for the images. Taking a hacksaw to my tube is not an option i want to consider.

So i think i'll just invest in a low profile focuser, and i'm sure i can live with doing manual focusing.

Rich.

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So i think i'll just invest in a low profile focuser, and i'm sure i can live with doing manual focusing.

Rich.

It may be worth checking that the low profile will get you into focus by removing the focuser and trying to judge where the focus point actually is. Just because it is low profile doesn't guarantee it will focus.....
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