Help - Telescope setup question

[symbiosis]

Hi all

I recently purchased a very cheap Tasco reflector model 302012 (D=114mm F=900mm) with a (fairly decent) EQ2 mount. The scope came with a 0.965 eyepiece fitted in the focuser. The focuser had a plastic ring that came out that appeared to be an adapter to 0.965" from 1.25" - this seemed even more likely as my 1.25" EPs fitted perfectly once I had removed it.

However, when I tried observing the full moon using my 1.25" EP, the image lacked any real detail (compared to my super cheap Celstron 60az using the same EP).

I'm assuming that I should get a better image from the larger Tasco than the Celestron so any ideas what could be causing this? Might it be that it should be using a 0.965 EP (not sure what using a 1.25" EP with a 0.965" focuser would do) or might it need collimation?

Any help much appreciated

[Bizibilder]

Looking at the full Moon can often seem lacking in detail as there are no shadows (the Sun is overhead, if you were standing on the Moon) and it can be difficult to even see some craters! Secondly the Full Moon is very bright and this will also affect what you can see as the brightness will swamp any detail that is there. It may be that the smaller scope was producing a much fainter image allowing you to see more detail.

[symbiosis]

Thanks Roger - interesting points that I hadn't considered. As you say, I couldn't even make out any craters with the Tasco but could see a lot more detail with the much smaller Celestron. Perhaps I need to try it out with some fainter objects

[kenmyers]

possibilities:

1 Are you in focus?

2 Colimation is well worth doing and very easy.

3 Dew/misty eyepiece/main mirror = leave scope outside for longer to cool down and demist itself.

4 Check eyepiece quality under a lamp checking for defects and dirt.

5 you are using the wrong eyepiece for the moon.

What size is the eyepiece you are using? it should have it'S focal length written in mm's. If it is around 20mm you should see the moon brilliantly clear and most of it in one frame. If it is around 10mm you are very zoomed in and the image will be harder to focus but take some time with it to get it right.

any details you can provide will help us help you better.

[kenmyers]

ps your new tasco should be a magnitude of order better than the celestron you have. keep at it.

[symbiosis]

Thanks Ken, in reply:

1 Are you in focus? Yes

2 Colimation is well worth doing and very easy. Might need to give it a go......

3 Dew/misty eyepiece/main mirror = leave scope outside for longer to cool down and demist itself. None noticed

4 Check eyepiece quality under a lamp checking for defects and dirt. EP gave good clarity in a different scope

5 you are using the wrong eyepiece for the moon. This was a 20mm with a moon filter, also tried with a 6mm and had the same result, clear and sharp with the celestron but very washed out with the Tasco

At the risk of being dumb, I was a bit concerned that I was trying to use a 1.25" EP in a 0.965" focuser but I think the focuser just had a 1.25 - 0.965 adapter ring in it. If a 1.25 EP fitted it, then I guess this wasn't a problem?

[symbiosis]

Perhaps I should also add that I used the same 20mm EP in the Tasco in the day and had it focused in on a few rooftop birds half a mile or so away and it looked fine then

[Moonshane]

could it be the quality of the diagonal? perhaps the TASCO one is poor and the other a lot better? if there's a way to swap them across try it? perhaps you could at least try the 1inch one in the celestron with the adapter on the nosepiece of the diagonal so it will fit the celestron drawtube?

[kenmyers]

You wont have any problems using the 1.25" eyepieces in the 0.965" focusser if you have the adaptor. It is litterally only a problem if the focusser is too small to fit them in, but you are ok.

If you are getting clear views with the same eyepiece in another scope - panic.

joke

DONT PANIC

Try collimating your new scope and/or check how clean the secondry mirror is. (look in the focusser without the eyepiece in place)

oooooooh... take off the moon filter!(it might help a little untill you figure this out) and try pulling back the focus all the way and then slowly bring it back in to clarity if possible. You should see some ring pattern before focus, ie the moon/star has a hole in it surrounded by a disc of light. this is a way to check your colimation.

hope some of this helps.

[symbiosis]

Thanks for the suggestion Moonshane but I dont think the Tasco reflector has a diagonal

[kenmyers]

Perhaps I should also add that I used the same 20mm EP in the Tasco in the day and had it focused in on a few rooftop birds half a mile or so away and it looked fine then

Any possibility that a diffuse cloud was in front of the moon blurring it?

[kenmyers]

could it be the quality of the diagonal? perhaps the TASCO one is poor and the other a lot better? if there's a way to swap them across try it? perhaps you could at least try the 1inch one in the celestron with the adapter on the nosepiece of the diagonal so it will fit the celestron drawtube?

It is a Newtonian scope he is using. Diagonal not needed.

[Moonshane]

Thanks for the suggestion Moonshane but I dont think the Tasco reflector has a diagonal

oops, sorry I read refractor. ignore me completely then!

[symbiosis]

PANIC! LOl

Thanks again Ken, I will certainly try your suggestions.

Actually, I am feeling a little panicky regarding collimation having never done this before - any good guides for a reflector that you would recommend for a complete novice?

[symbiosis]

Guess its possible regarding the cloud

[kenmyers]

I found some great videos on youtube on how to collimate. Their are two ways/tools for doing this.

One called a cheshire collimator and the other called a laser collimator.

The laser is simple and very effective and super fast, but more expensive.

The cheshire is litterally an old negatives film casing with a hole pierced in the centre.

I can't link you as youtube is blocked at my work.

[symbiosis]

Thanks again, will check youtube

[symbiosis]

It appears that my scope DOS'NT have a center mark on the primary mirror. Does that mean I need to remove it and make one on it to use the cheshire method?

[symbiosis]

Thanks for the help all, specially Ken

I know have a center spotted and cleaned primary mirror that's also collimated - now I just need a clear night to test,,,,,,,,,,,,

[symbiosis]

The mirror was rather grubby so a clean could only help

[ronin]

Isn't the mirror on these spherical?

If so the image will not be overly sharp to start with at f/7.9.

[symbiosis]

Yes the mirror was spherical buy surely it should still produce better images than the Celestron?

[symbiosis]

Pleased to say that I just tried it out again and (despite the moon being behind clouds) the image was fantastic! looks like the collimation and cleaning did the trick

Thanks for everybody's input

[kenmyers]

Brilliant. What method did you use to centre spot the mirror?

I guess you followed a guide on cleaning the primary?

Very brave, well done.

Enjoy your views.

Edited October 31, 2012 by kenmyers

[symbiosis]

Thanks Ken, yes I found a few guides on mirror cleaning and followed those. The trickiest part was actually releasing the mirror assembly from the tube, there wasn't a guide for for my particular scope and it had a few oddities that others I looked at didn't seem to have. I recorded it so will put up a quick youtube video for anyone else wanting to do the same with my particular scope..

I marked off the center using a (non permanent) board marker pen and then very carefully centered a ring binder circle over that, it was actually not far off perfect alignment when I put it back together so I only needed to tweak it a little.