200P & EQ5 for AP - Will I get away with it?

[Catweazel]

Hi CW just to comfirm for the two weeks I owned the scope it was very easy to attach my Canon D1100, my t-ring screwed direct to the upward aspect of the camera adaptor you showed above, and the downward aspect fits into the 2" focusser:) The problem I had was getting focus as the CCD chip in Dslr cameras is roughly 40mm behind where the front of the camera attaches to the scope, hence you need to focus in an extra 40mm to achieve focus and there isn't enough travel. You can get around this lack of travel on the focusser by attaching a barlow, but if its a 2x Barlow you instantly turn your scope into an f/10 which is great for Moon mosaics, and planetary webcam imaging but f/10 is too slow for DSO and also the field of view is too narrow. The way around this is too move the primary mirror forward a bit, then you can achieve focus at f/5, happy days:D as I mentioned to you when we met, I'm not sure how much to move the primary forward?? QM over to you matey:D

p.s. have you had the 200p out for visual yet CW??

Hi Starfox! I have had the 200P out for visual and all seems ok. I suspect it may need collimating, but I have no idea how to do it, so will get a cheshire and try to check it out. Only got to look at Jupiter and Orion Nebual so far though; been cloudy ever since

I remember you mentioning the idea of moving the mirror forward for AP. I would guess that I need to move it 40mm, but that's probably too obvious. Hopefully someone will come along here and help me out (again!) I have also heard tales of extention tubes for this purpose, but don't really understand that either. As you can tell, I'm going into this with my eyes wide open

[Chris]

Hi Rik, I sold Catweazel the blue tube 200p that came with the mk1 HEQ5 I wanted, the guy told me he bought the setup about 4 years ago. Can he bring the primary forward for DSO, or does he need to swap out the focusser, anyone?

[Chris]

Hey CW, I did a rough collunmation when I had it out by defocussing a bright star so you get the doughnut effect, then adjusting the 3 screws behind the primary untill the inside circle of the doughnut was concentric with the outside circle. The 3 screws are behind the round plate at the bottom of the tube, there is also a locking screw for each of the 3 screws to help keep collumnation. I've heard that laser collumnator are good, check out Astronomy shed collumnation tutorial on youtube, he covers collumnation on the 200p in as much detail as humanly possible:D

[Quatermass]

Also check out Astrobabys web site it has lots of great info. I dont think you need to move the mirrors to get the camera focused but the 1000d is a bigger body then the 350d so you may need to just buy the correct adapter for it. Harrisons should be able to advice you also the Astronomiser site is very helpful.

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[RikM]

Edit: Unless you can find an adaptor that fits, moving the primary up in the tube is probably the cheapest way of achieving focus but I am not sure exactly how to go about it. With the newer scope I would take the mirror cell off, shorten the tube then dill new holes and refit the mirror cell. I expect a quick investigoogle will bring up an illustrated tutorial how to go about it.

A Cheshire eyepiece is far more cost effective and likely to be more accurate than a laser for collimation. People often think that lasers must be something special but unless well collimated themselves (not always possible with budget ones) they are likely to do more harm than good because you will stick the laser dot in the doughnut in complete confidence and miss-align everything because the laser itself is out of whack.

[Chris]

Would this work? calculate the distance the primary needs to to be moved up the tube and then build up an 8" plywood circle to the thickness of that distance then place it between the primary and the mirror cell??? this sounds too simple it must be wrong:D If this works then the process is easily reversable to go back to factory settings:)

[Catweazel]

Wow! This is getting complicated, 2 hours ago I was expecting to just connect the camera with the T- ring, I don't think I'm up for drilling the tube and such like, I'm really not technically compitent enough for that at all It might be easier (and much cheaper) to give it a miss altogether for now. I can see now why they say imaging is a competely different game

[Quatermass]

I really dont think it needs mirrors moving about to get focus the cannon 350 is not that much smaller then the 1000d just the right adapter should work surely? or am I missing something. Once the camera is on and if you have single or dual axis motors and a home made bahtinov mask your pretty much good to go.

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[Quatermass]

Is the focuser the standard one one a 200p or different? Getting a camera on it should be the least of your problems I would have thought.

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[RikM]

All the Canon EF and EF-S camera bodies have the same spacing between the flange and the sensor, meaning they need the same focuser travel to reach focus. If there is a short enough adaptor, that will also fit in the old SW focuser (which doesn't accept standard 2" adaptors directly into the draw tube like the new black diamond ones), then it ought to work. I don't know of such an adaptor but there might well be one available.

Worth trying a forum search because this topic comes up a lot. It was a big problem with the blue tube SW Newts and eventually led to the new focusers on the black diamond scopes with 'direct SLR attachment'.

[Catweazel]

I really dont think it needs mirrors moving about to get focus the cannon 350 is not that much smaller then the 1000d just the right adapter should work surely? or am I missing something. Once the camera is on and if you have single or dual axis motors and a home made bahtinov mask your pretty much good to go.

Ok QM, as I have the T-Ring on the way, I will give it a try and see what happens, perhaps we can leave the subject of bahtinov masks for another day

many thanks folks for all of your help with this today

[Chris]

Hey QM:) Rik mentioned that the focusser has changed over the years on the 200p and I know you have the new black diamond 200p not the blue tube CW has, so I'm not sure a slight adjustment between Dslr body widths will do it? the adaptor might work though like you say, would an extension tube adaptor effect the FOV or F/ratio though? Putting my old engineering hat on I'm wondering if building up a plate to put behind the primary would work as it might be a cool little mod, and a lot easier than sawing down the tube and re-drilling, as you would have to brace the inside of the tube to stop it from distorting when sawing for starters.

[RikM]

http://stargazerslounge.com/discussions-cameras/171644-not-enough-forward-focus-eos-1100d-200p.html

You would need one of the new 2"-1.25" adaptors that unscrews to leave a T-thread, but if your focuser is like the one in this other thread, the new adaptor might not fit perfectly.

I don't think there is any way to put a board or something between the mirror and the mirror support but it might be possible to use longer adjuster bolts. I don't know how stable that would be. Mirror shift is also not good for AP.

[Chris]

Yeah I've just read that someone moved there mirror forward for imaging by about an inch using longer adjustment screws and longer and stronger springs.

I've looked at the design, and my idea would involve longer versions of the c-shaped mirror clamps from a larger mirror set, and the board would go behind the mirror effectively just adding thickness to the mirror, so it could be done but it would would be a bit stupid when you can just use longer screws like you suggest But from what I've read this would be stable if you used longer and stronger springs.

[Chris]

One last silly idea:) could you use a coma corrector on the focusser and kill two birds with one stone, i.e. it would add distance between the secondary and focusser and have the added bonus of correcting coma?

[Quatermass]

Sorry Im completly confused now my focuser is easy to fit,the canon t.adapter goes on camera then that lot goes onto this bit that im holding, after the barrel is screwed off. simples.

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[Quatermass]

I spend way too much time on this forum becoming addicted, is there a known cure

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[malc-c]

On a 200P using the T-ring on the 2" adapter as per QM's post works fine with my Canon 400D, and I can't see why it wouldn't do so with any other Canon dSLR.

[RikM]

Guys, the old blue tube focuser barrels and adaptors are a different design to the new ones. The old 1.25" adaptor is a high profile one that doesn't unscrew

and the actual focuser barrel is larger than 2" so a coma corrector will need to be shimmed or it will slop around.

[Quatermass]

Ah I see well in that case I would get a new focuser I have thought of getting one for my telescope as it slips sometimes when im adjusting stuff.

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[RikM]

Ah I see well in that case I would get a new focuser I have thought of getting one for my telescope as it slips sometimes when im adjusting stuff.

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So would I.

[Catweazel]

Guys, the old blue tube focuser barrels and adaptors are a different design to the new ones. The old 1.25" adaptor is a high profile one that doesn't unscrew

and the actual focuser barrel is larger than 2" so a coma corrector will need to be shimmed or it will slop around.

Morning guys

Yes, mine is like the one in this picture!

Having slept on it, I think that I will forget imaging with the 200P; I didn't buy it for imaging and it was just an afterthought really. I think that once I start replacing focusers etc, and taking into account that the tube is on the cusp of effectiveness on my EQ5, then I may as well wait for a while and invest in a 2nd hand ED frac; a lightweight one would possibly tolerate the EQ5, but if not it will have to go on the back burner, as I can't afford a stronger mount in the medium term. Hey ho!

Anyway, thanks for all of your comments and effort, they are very much appreciated CW

[Chris]

Yeah I think you have the right idea CW to replace the focusser it would cost 100 pounds new, and for 100 pounds you could get an f/4.9 ST80 and a fringe killer/semi apo filter to practice AP as this would be better tracking wise with your eq5, and tracking is key. Then if you find that you get the imaging bug sell some kit and get the ED glass or HEQ5 (or both), if you get really into imaging you might want to keep the ST80 as its an excellant guide scope by all accounts, well this is one scenario? I would keep your 200p for your visual use as I know your into visual.

[Quatermass]

Agreed:)

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[Spikey]

Keep your eye out for a second hand low profile focusser for the 200p they do come up occassionally.