A FOCUS PROBLEM WITH MY STARTRAVEL-120 (AZ-4)

[menacegtr]

Hi again to all of you. I have today 17/2/ all my parts and the scope delivered , but I have an issue already. These are the parts I have

ST 120mm scope + eyepieces that came with it + the Skywatcher 45° Erecting Prism

Skywatcher 2" Di-Electric Star Diagonal

Skywatcher 45° Erecting Prism 2"

Celestron X-Cel LX Eyepieces 1.25" 9mm and 25mm

Revelation Astro 2.5x Barlow Lens 1.25"

AZ-4 Steel Mount

Ok the problem, when I am using the scope with the Skywatcher 45° Erecting Prism and any eyepiece I have no problem seeing my target. I used an electricity pylon about 2/3 miles away and was able to get the image right in close especially when using the  X-CEL 9mm, barlowed even closer, so I thought that's nice. so I switched over to the Skywatcher 45° Erecting Prism 2" but could not get the same target to focus at all. The focuser wants to move  more towards the stop at the very start of the travel but is not in focus which I find very strange. The only time it will foces is objects 50/100 meters away. All the parts plus scope were purchased from Rother valley optics. I rang them a few days earlier to make sure what I was buying would all be suitable for the scope. I was very interested in swapping out the included Skywatcher 45° Erecting Prism for the much better or so I thought Skywatcher 45° Erecting Prism 2" version as I wanted to use 2" eyepieces and the chap on the phone said yes that would work miles better than the stock 45° Erecting Prism. Anyway that is my problem it will not focus on far targets at all. Now the Skywatcher 2" Di-Electric Star Diagonal works the same as the standard 45° Erecting Prism but much brighter and clearer and left to right image but it works and I don't use hardly any extra focus between this and the 45° Erecting Prism. so am I doing something wrong or has the dealer not told me the whole story. I suppose the other reason I purchased the Skywatcher 45° Erecting Prism 2" is the use of the compression ring to not mare up my nice new Celestron X-Cel LX Eyepieces. I have made a new friend on this forum to try and help me out but I thought I would put it out to see what others might suggest. I hope I have explained it properly to you all and hope to get help.

                                          Kind regards. Dave

Just tried something, I unscrewed the 2" to 1.25" converter of the end of the focus barrel just to see if I can get am image through the Skywatcher 45° Erecting Prism 2". I carefully placed the 45° Erecting Prism 2". into the focus tube and inserted it all the way being careful not to go to far, I can now focus while carefully holding it on a 2/3mile target with about 20mm of the focus tube outwards, so obviously the 45° Erecting Prism 2". is not going in far enough for it to work correctly. I can see the target clearly but its obviously not the right way to go about it having to hold it carefully through the tube without scratching up my 45° Erecting Prism 2". Have I been sold something that is not compatible with my ST 120mm scope. I have rang today 18/2/ Rother Valley Optics and the chap on the phone says he has never heard of my problem and has sold many 45° Erecting Prism 2". He says he will get back to me latter today, I hope he does. The 45° Erecting Prism 2". was £99 delivered so I am not to happy with my first delving's into this new hobby. So again I hope somebody here can please help me out.

                                                                        Thanks in advance. Regards. Dave:

Another edit, will a Skywatcher Dual Speed 2" Crayford Focuser For Refractors give me more focus headroom to get the Skywatcher 45° Erecting Prism 2" to focus  without going beyond it stop of travel

                                           Regards. Dave:

[Cornelius Varley]

The problem might be that you are using an adapter between the diagonal and focuser draw tube. You mentioned removing the 2"-1.25" eyepiece adapter and holding the diagonal behind the tube (if I understood you correctly) and achieving focus. Could you post some photos of the setup with the problem. There might be something wrong with how you have set up the telescope that might be more obvious in a photo. If no one else has reported this problem with this combination of telescope and diagonal then it might a fault with the set up.
 

[menacegtr]

@Cornelius Varley I cant pics small

enough to post on this site, but I have just had a phone call from Rother valley Optics and they say I need this item to lengthen the focus draw tube, would you agree

http://www.rothervalleyoptics.co.uk/antares-2-twist-lock-extension-tubes.html.

       Regards. Dave:

[menacegtr]

Sorted the camers out the first pic is the standerd Skywatcher 45° Erecting Prism And the second is with the Skywatcher 45° Erecting Prism 2" and focused right up but not in focus. In this pic if I remove the 2"-1.25" eyepiece adapter then I can insert the Skywatcher 45° Erecting Prism 2" by hand directly inside the draw tube. That is the only way to get focus unless as stated I use the recommended Antares 2" Twist Lock Extension Tubes

                        Regards Dave:

[menacegtr]

and this is without diagonal. Sorry for slight lack of focus

      Regards. Dave:

[Ricochet]

Are you saying that to achieve focus you have to remove the black 2" adaptor (shown in your last photo) and just hold the prism inside the silver draw tube? If so it sounds like the tube is too short not too long.

[menacegtr]

yes that's what I am saying

[menacegtr]

is there anyway I can still use this Skywatcher 45° Erecting Prism 2" on my scope. The dealers I have rang say yes it should its just a 2" erecting prism. What am I doing wrong

                                  Regards. Dave:

[Cornelius Varley]

I'm not sure the extension tube would work. An extension would be used if you couldn't wind the draw tube far enough outwards to reach focus, this is usually the way to get a camera to reach focus if connected directly onto the tube. If the problem is that the diagonal is too far away from the draw tube and the tube cannot be wound in any further then the problem could be elsewhere. If your 2" 90 deg diagonal works but the 2" 45 deg erecting prism doesn't then the problem could the the erecting prism. This might have a longer focal path than the normal star diagonal and so required the draw tube to be wound further in to compensate for the increase in the length. Another thing to consider is the eyepiece. Is the problem with the 9mm or with both ?

[menacegtr]

I am just wandering if the Dual-Speed 2" Crayford Focuser for Sky-Watcher Refractors might do the trick, it looks like it might draw it in further. Just a thought. The only other solution I can think of is adapting a shorter 2"-1.25" eyepiece adapter. if you look at the picture without the diagonal fitted you can see that it sits quite further out, if I could find something that would screw on the tube end and give me enough purchase to be tight I could have the piece that the diagonal fits into much closer to the tube if that makes sense. Like I said if I take the 2"-1.25" eyepiece adapter of I can drop the Skywatcher 45° Erecting Prism 2" much further into the tube and would hopefully be able to clamp it down as usual with either a screw or twist lock mechanism. surely there must be something I could screw on the end to bring it in closer to the tube

                                          Regards> Dave:

[Cornelius Varley]

If the dual speed focuser is sufficiently shorter then it might work. The best thing to do now is contact a dealer and find out the overall length of the focuser fully wound in. 

[DevonSkies]

Do you really need to use a 45 degree prism (e.g. for terrestrial viewing)? If you're only using the scope for astronomy, personally I would return the 2" 45deg prism and just use the 2" mirror diagonal. The reversed image is not a problem for astro use.

[Alan64]

I've no experience with 45° Amici-prism diagonals, nor any 45° diagonal for that matter.  I do have a fully-corrected 1.25" 90° Amici-prism diagonal for daytime/terrestrial use.  Is it that you're wanting to use 2" oculars for same?

It could be that only 2" oculars will come to focus with it.

In my experience, no diagonal, especially a 45° terrestrial, was worth having to replace the focusser, except in the case where I converted a refractor from .965" to 1.25".

[menacegtr]

Yes I wanted to use 2" eyepieces with my Skywatcher 45° Erecting Prism 2" and its a better quality upgrade then the standard one, that's why I bought it. In the mean time I have been in tough with a Steel, aluminium machine fabricator and he is going to make a custom 2"-1.25" eyepiece adapter to just fit behind the tube barrel and to screw right the way onto the threads so I can get all the back focus that I need. It will be a good 1/2" to "3.4 Three Quarter Inch shorter. That will give me plenty more inward without affecting outward focus. Thanks to my main man for all the help, advise, and tea, you no who you are. And your wife is lovely.

                                          Dave:

[Alan64]

Yes, of course, but will you be using the 2" 45° diagonal at night?

Incidentally, how do you like the AZ4 so far?

[menacegtr]

@Alan64. No at night time I will be using the Skywatcher 2" Di-Electric Star Diagonal. And also the reason I went with the Skywatcher 45° Erecting Prism 2" is 1, obviously it is a massive upgrade to the standard Skywatcher 45° Erecting Prism. 2, I can use 2" eyepiece's, 3, as somebody suggested why not just use the Skywatcher 2" Di-Electric Star Diagonal, but I would not last to long looking strait down at a top down view point, I suffer bad back problems, and lastly I just like nice things, and hopefully they can carry me over to different scopes latter in life. And as for the AZ4 I think it has, will prove to be the upgrade of the day. The only thing I might do to it is have a duplicate rod made to move the left to right motions a bit easier (not sure what you boys call that). I will get the guy who is milling me a new 2"-1.25" eyepiece adapter to tap out a thread and a nice chunky piece of rod. I am just toying on that at the moment. After playing with my friends scope mount today 19/2/ I am extremely jealous and very envious at the amount of control he has. I am not sure what the make was but it was on the same legs as the AZ4 but built like a tank.

                                                   Regards. Dave:

[brantuk]

It was the Skytee-2 mount Dave - and the scopes were Skywatcher Maksutov 127 and William Optics Megrez 72FD.

[Alan64]

15 hours ago, menacegtr said:

@Alan64. No at night time I will be using the Skywatcher 2" Di-Electric Star Diagonal. And also the reason I went with the Skywatcher 45° Erecting Prism 2" is 1, obviously it is a massive upgrade to the standard Skywatcher 45° Erecting Prism. 2, I can use 2" eyepiece's, 3, as somebody suggested why not just use the Skywatcher 2" Di-Electric Star Diagonal, but I would not last to long looking strait down at a top down view point, I suffer bad back problems, and lastly I just like nice things, and hopefully they can carry me over to different scopes latter in life. And as for the AZ4 I think it has, will prove to be the upgrade of the day. The only thing I might do to it is have a duplicate rod made to move the left to right motions a bit easier (not sure what you boys call that). I will get the guy who is milling me a new 2"-1.25" eyepiece adapter to tap out a thread and a nice chunky piece of rod. I am just toying on that at the moment. After playing with my friends scope mount today 19/2/ I am extremely jealous and very envious at the amount of control he has. I am not sure what the make was but it was on the same legs as the AZ4 but built like a tank.

                                                   Regards. Dave:

Hi Dave,

The Skytee-2 is also known as the AZ5... http://www.teleskop-express.de/shop/product_info.php/language/en/info/p4537_TS-AZ5-Alt-azimuthal-Mount-with-tripod-and-fine-adjustment.html

...and the next step up from the AZ3 and AZ4.  The Skytee-2 is larger and somewhat heavier, of course.  Both FLO and RVO carries it.

The mount-head alone, without the tripod, doesn't seem that it would weigh much more than that of the AZ4, perhaps, and at 5 kg.

Regards,

Alan

[menacegtr]

Hi to you all, just an update as to my problem with inward focus with my Skywatcher 45° Erecting Prism 2". The new part has just arrived back, it took just over a week as my fabricator was busy doing other jobs. He has made a great job of making me a new adaptor. As you can see from the pics, he has cut the size nearly in half so I have gained all the inward focus I want and more. As the photo shows the smooth part butts right up to the focus tube and the knurled piece screws secularly on to the focus tube. I am very pleased with the results as I now can keep the much better Skywatcher 45° Erecting Prism 2". for daytime use

[menacegtr]

[menacegtr]

Also in the 3rd picture I have acquired a red dot finder from a friend who said he no longer uses his telescope. He said I could have it but I said I must give you something for it, he wanted £8 for it. I don't no if it is any good for my telescope but he seems to think it will fit onto my focuser. The finder did not work but a new battery has fixed it. I do not no what kind of finder it is as it has no make on it but its as he said not been used much and is in mint condition and made of aluminium. It has 4 sight reticules that you can switch from the back and comes with a nice rubber sleeve for the glass bit at the front to protect it. The only problem I have is there was no mount for it as he mislaid it but my fabricator friend has it in his workshop and will make me one out of a billet of aluminium so it should slide onto the focusers, (hopefully). that's all for now.

                                           Regards. Dave:

[brantuk]

Excellent job Dave - glad your mate has sorted out the adaptor and the 45^o diag now works for daytime use.

[menacegtr]

Hi Kim, hope your ok. I am testing now and I have loads more inward focus, my man has done a great job on the adaptor. Any idea on the red dot finder, which model it is and is it any good for my scope? it looks and feels way better than the standard one that came with the scope.

                                           Dave:

[brantuk]

Yup - your multi reticule red dot finder is the same as the one I have on my WO Meg72 - they're very useful little finders but I'm not sure exactly what they're called in terms of model name. Just WO RDF as far as I'm aware - also you might have a clone of it cos several scope producers use them.  

[Paz]

On 2/28/2016 at 15:47, menacegtr said:

The only problem I have is there was no mount for it as he mislaid it but my fabricator friend has it in his workshop and will make me one out of a billet of aluminium so it should slide onto the focusers, (hopefully). that's all for now.

                                         

I'm not certain as I don;t have that RDF but you can get a mount from astroboot - either the RDF red dot finder pedestel or the RD finder to QR - if you have a look you might be able to see if either would be the right fitting - they're up for only £3.

p.s. where your fabricator makes things, what roughly is the going rate to have things like that adapter machined up for a customer - I can think of lots of SGL'ers imagining the various adapters and widgets they would like to have made up if it were possible!