Boros

As a follow up to my previous thread re 'focuser issues with Skymax 127 Mak' I have tonight discovered a possible contributory factor. I decided to do a 'star test.' First one I did using a pin hole in a black disk taped over an led torch came out like this: Which I thought looked okay, but later on this evening I decided to try it on a real star and I was slightly taken aback at the result. I didn't manage to get a photograph, but I've altered the image below to be as close to what I saw as possible. Can anyone explain what might be going on please as this doesn't look like any pics of uncollimated scopes that I've seen. Could the difference between them be due to the fact that for the first one, the focuser was wound almost as far back as it would go as my artificial star was just up the garden a bit, so presumably the mirror would be 'locked up' at that point. The second one was unfocused on a star, just thinking it might be something to do with the position of the mirror in relation to the rod, and that something is happening to the mirror as it travels up the rod, causing the distortion!! I don't know just a complete guess on my part! But something definitely looks amiss.

I tried the sponge thing, but have to confess didn't like the soft feel, just felt a tad vague to me.

Hi I've found like others that the small diameter focus knob on the Skymax 127 is not conducive to achieving accurate focus. I fully intend to add an auto focuser but in the meantime decided to make my knob bigger, er hmm, you know what I mean! I've seen various methods, using clothes pegs, Nutella caps etc, but I wanted something that didn't look quite so 'Heath Robinson' so briefly here is what I did. The idea was to use the existing knob to form a female mould using car body filler inside a larger diameter cap. I managed to find an old Tamron adaptall mount cap, and a spare cap which I think came off an old diagonal, this proved to be almost an exact fit inside the Tamron cap. I decided to cover the knob in clear tape to protect it and make it easier to remove from the filler. I then filled the diagonal cap with the car body filler, inserted the focus knob, centered it, then set aside to harden. Once hardened it was easy enough to remove the knob, then remove the excess filler, tidy it up and make black. I also added some black electricians tape around the central part of the cap, not necessary but I think it looked a tad tidier. After that it's just a matter of securing it inside the larger cap with epoxy resin. It's a nice snug fit over the knob, but with a slight smear of vaseline on the rubber it slides on and off more easily. Overall, functionally I think it's a big improvement and it doesn't look too bad either, although I may add a plain plastic disc over the 'Tamron' printing just to tidy it up a bit.

Hi Magnus No I don't intend to do it now, it was just for future reference, but very interesting to know that it's okay to use acetone on the mirrors.

Thanks so much for that information Magnus, your post/thread on the 180 is superb, such a lot of time and effort into producing it, I'm sure it's been great help to many with questions or issues with these scopes. If I do eventually decide to venture inside the tube, these instructions will be invaluable. One question at this point, not related to the focuser but the secondary mirror, I've been led to understand that it's best not to try and clean these, so can I ask what your method, cloth and cleaning fluids were to complete that task? Many thanks for your help.

Hi Thanks, I had already done that, I removed the knob, shaft had small indents where the screws had been tightened onto, so rotated and tightened in to fresh section of the shaft. But that hasn't made any difference. Thanks for the link, it seems a task not to be undertaken without good reason, especially without the accompanying photographs! However I did try to unscrew the back plate just to see if it would move, but failed miserably. Also I did find this article : http://scopeviews.co.uk/SW127Mak.htm Where it does touch on the same issue I'm experiencing, unfortunately he doesn't explain or delve into this problem any further than the following: The focuser is typical of a Maksutov – a knob protruding from the back-plate moves the primary mirror. This arrangement gets a lot of bad press because in some cases you get a lot of image-shift when changing focus direction That being the case I'm surprised there is not more to be found documenting the problem or reports of others with the same issue.

Since I've had this scope which I bought s/h I've felt that the focus adjustment wasn't quite right, but it seems to be getting worse, and it's proving more difficult to nail focus than I think it should be. If I go past focus then wind it back, I seem to have to turn the knob back much further than where focus actually was to get past focus and bring it back again, so I get the impression that the position of the knob in relation to it being in focus seems to change. Also sometimes the change from being out of focus to being in focus is more of a step than a smooth transition. I have checked that the knob is not moving on the shaft and the grub screws are tight. Have to say it's quite annoying and getting critical focus isn't the easiest task at the best of times anyway. Any ideas or remedies greatly appreciated.

Thanks for suggestions, another option has cropped up, if I fit tube rings I should be able to rotate the scope to the correct orientation, I think I quite like that idea, it's non invasive and can be changed back in the future if required. So just need to find a set of rings to fit. From what I can gather from other posts the Skywatcher 140mm rings 'might' fit. Bit of debate as to what the actual inner diameter is 140- 143mm? I have measured my tube and it's 142.8mm so if they are 143mm+ they should be okay. Anyone actually tried to fit these rings?

Yes I was aware that is the case, but as I said I had intended to do the mod which rotates the rear plate and that would alleviate the issue, but I now can't find the article explaining the procedure. I don't know if it's straightforward and don't want to risk messing up the collimation. Really was hoping someone would have done it and could explain the process. I have a decent red dot sight, so spending on another one is not an option. Thanks Rob

Hi all Hoping I can get some questions ironed out relating to the mounting of my 127 on an AZ GTi which I've just bought (separate purchase). I have searched the subject but am left with a few questions. When the 127 is mounted on the AZ GTi , it's on the left side of the mount, which is fine because I am left handed and prefer it being on the left, but it does pose a problem for me, my 127 has the mounting rail on the underside, so when it's mounted on the AZ, the focus knob is now directly behind the diagonal, which is a tad inconvenient, but worse still is that my Baader red dot sight would be in an impossible position down to the left about 7-8 o'clock. My intention was to hopefully rotate the backplate by slackening the screws so it could be rotated to the right, bringing the focus knob and sight mount back to their normal positions. I read an article somewhere about doing this, I can't find it now, but am having second thoughts anyway, just concerned I'd be opening the proverbial 'can of worms' by attempting it and upsetting the collimation . Has anyone done this 'mod' is it easy enough to do, and does anyone have a link to the article? Or any other suggestions how to get round this issue. Thanks

Hi The diagonal it came with is a rubbish plastic 90 degree mirror, not a prism, I alternated it with the one from the 102GT which is a 45 degree prism, and on checking it is indeed an amici prism, so that probably explains the vertical black line, thank you Vlaiv. I'll try rotating focus knob to it's extremes a few times, although it's had a good workout already, but I suspect that this is where the focus/ soft image issues are stemming from. If so and the focus racking doesn't help, then it looks like I won't be buying it! Thanks again Vlaiv and White Giant.

Hi I talked to my neighbour about his Bresser, he's not in a hurry to have it back so says I'm okay to do a few more tests on it. I had really clear skies this morning about 2am so had a good opportunity to try it on a proper subject. Did the star test and to be honest it all looked fairly concentric, but one thing I did notice was that the out of focus disc had a thin black line running vertically through the centre, this moved to either side if the disc was moved away from the centre of the frame, is this normal? Also I'm not sure about the focuser (is that a word?) First of all I never felt the images of Saturn and Jupiter ever got truly sharp and when trying to achieve focus if I went too far and had to bring it back a tad, it went way out of focus so had to wind it back really far then try again, so I basically have to wind it to achieve focus first time, can't just get it close and jiggle it a bit. it's impossible to fine tune the focus, it can be almost there, I'll move it just a tiny bit, but it jumps out of focus to almost a doughnut, so have to wind it way back and go in again. Anyone had any experience of these issues?

Okay all thanks for your advice, I'll update when I have made some progress.

Hello Gfamily, thanks for your thoughts, I totally understand what you mean and I will try what you have suggested, but just taking the results from the mak on their own, they are not good. Some Maks like the Celestron C90 are used as spotting scopes presumably during the day, this is unusable for that purpose. I've read that Maks are supposed to have very sharp optics, this is far from sharp. But as I say I'll give it another chance tomorrow, redo the star test and use different lenses as you suggest, but I've a funny feeling I'll be handing it back to my neighbour. Shame really as I'd hoped it could have been a more user friendly scope than the 102GT. Thanks for all the input from everyone.

Hi Yes I tried it with 2 different diagonals, the one that came with it, a mirror one(cheap rubbish plastic) and the one from the 102GT which is a prism, not much to separate them to be honest. And both diagonals with 2 different eyepieces. The camera was prime focus using a barlow (without the lens) Image was soft viewing through eyepiece and the camera lcd and the camera images are also soft and just look slightly out of focus. I went back and forth with the same setup between the 102GT and the Bressier and each time the image from the 102GT was noticeably superior, more contrast and distinctly sharper, the Bressier just looks soft no matter what I did. Conditions were fine, daytime and viewing brick chimneys about 100yds away.

Okay, well the middle image is the least defocused, and that doesn't look too bad, but I think I might do another test as it looks like that one might have been flawed. After looking at your link White Dwarf it looks like I might be opening a can of worms by attempting to collimate this. If the second test shows the rings to be fairly concentric, is there anything else that would cause the image in the eyepiece to be soft and also prevent me from getting sharp images from the camera?

Hi White Dwarf I never took the scope outside, the moon shot I did the other night with the 102GT was taken from inside the house with the patio door open, and the test I did with both scopes was done the same way, I probably messed around with them for a good 1 1/2 hours so I don't think temperature could have been a factor. I think your right, I do need to keep the refractor as well. Anyway I've just done the star test with the following results. The first image is out of focus on the close side, the second image is just out of focus on the close side and the 3rd image is way out of focus on the far side. Interestingly when I took the first pic it appeared to be not too bad, but as you can see when the out of focus was transferred to the far side it definitely looks to be out of alignment, to my eyes anyway, can anyone enlighten me as to what it is and the remedy please. If it's collimation does anyone have experience of doing it on these Bresser Maks, I've searched online but can't find anything. There is 3 oval holes with 2 screws in each, but what they do is anyone's guess. Thanks all for your help so far.

Okay thanks I'll try a star test, but the way the weather is I might have to come up with an artificial star!

Hi further to my previous post 'first telescope questions' on relating my experience with that first telescope to a neighbour, it turned out he had bought a Bresser Messier MC 100/1400 Maksutov about a year ago and had hardly used it (seems a common story!) and he was willing to sell it. Now this seemed an ideal solution, a much smaller package that wouldn't be as unstable as the 102GT, easier to use generally, more portable and I could mount it on one of my heavy Manfrotto tripods. So I borrowed it off him and tried it out against the 102GT. But I have to say I was more than a little disappointed, the image appears to exhibit less contrast and definitely not as sharp. I used the same diagonal and 15mm lens in each one. I also attached my camera and I just couldn't get a sharp image at all. The adjustment allowed it go in and out of focus, but it never got truly sharp. Do you think these are issues with this particular Bresser or are they all likely to be the same?

Hello Thank you I really did. It is a good scope but just has the issue with the unstable tripod made worse by the long tube which necessitates extending the tripod to it's full extent where it's really unstable. Really need to find a way to stabilise it, I've tried weighing it down which improves it but not substantially.

Hello from another beginner! I'm more of a photographer to be honest, it's been my main interest for over 50 years, but I've never dabbled with astro or planetary photography. So this troubled spell we're going through seemed like a good time to give it a try. So being a Scot and not wanting to lay out lots of money on an initial foray into the sport, I kept an eye out for a s/h scope. I already did some research and decided that rightly or wrongly I probably needed to get a refractor or a maksutov. So after a couple of weeks I stumbled across this, it's a Celestron Nexstar 102GT with computerised mount. When I went to see it, the chap said he just noticed that the hand control wasn't working and he had just put new batteries in it, that's a bummer I thought! Anyway the thing is in immaculate condition, he had it advertised for £90, so I decided to have a haggle seeing as the mount was potentially smoked, and I got it for £50 sterling! Anyway on getting it home I immediately pulled and tested the batteries, they were fine so put them back and plugged it in and the handset immediately lit up and then proceeded to apparently work as it should, so who knows. I'd read the reviews on it and they are very mixed, some people seemed to like it others not so much. I couldn't wait to try it though and I managed to get some clear sky last night, just enough time to get my Fujifilm XT2 strapped on and a few pics taken before the clouds started rolling over again. I'd bought a T adaptor for it and it screwed straight on to the Celestron once I'd removed the the diagonal. For what I paid for it, it's an absolute bargain, and it could no doubt give me some serious enjoyment. I've attached a pic that I took last night and for a first attempt I'm more than pleased. However I do have a few observations that might mean it will be a stop gap. First one is the length of the tube, with the 45 degree diagonal you almost have to sit on the ground! This seems more suited to terrestrial use, when elevated to view objects in the sky it's unusable, and with the tripod fully extended it's even worse, you just need to breath on the scope and it induces the wobbles, I tried adding weight to the tripod it helped but not enough to alleviate the problem. So as far as I can see it does a reasonable job of imaging, but I'd need to make some adjustments and purchases, like a 90 degree diagonal which might help and definitely need to do something with the tripod, but keeping the motorised mount if possible. Any suggestions from you learned gentlemen would be appreciated.