menacegtr

Yes it was a direct replacement so it fits as the standard one did.

Thanks, that makes perfect sense. Why the hell didn't the shop owner tell me that when i rang up about compatibility with my telescope. I told him i already tried a different 45 erecting prism. Again thanks

Hi again all of you. It's been about 3 years now that i have owned my Startravel 120mm, i still love and use it. But, i am miffed as to why i cannot use something like an OVL 45° Erecting Prism 2" or anything like it. I don't have enough inward focus to find long range targets during daytime i just run out of focus. I am using a OVL Dual Speed 2" Crayford Focuser to replace the standard item. Why can i not get enough focus. i ordered an Ostara 2" 45 degree dielectric diagonal this week but again it does not work. I contacted the shop i purchased it from and he was very surprised and said he has never heard this problem, so i sent it back today. can anyone here please advise why i cannot use this type of 45 degree diagonal. Thanks for any advise, help

@wookie1965Nice to see this thread is still active.Your link you posted looks like the part i should have ordered way back. I don't have problems with inward focus anymore as a result of the altair astro 2" diagonal. Still loving my st120mm and the super crayford focuser.

Thanks for that. you can understand my slightly muted response to my new focuser even though I can use it perfectly well with my Diagonal I am always at the back end of focus, around the 1 mark or just under. It makes perfect sense how you can have way more focus. I have ordered one so I should look forward to extra inward focus should I need it, I hope it works as yours does. Thanks for posting the pictures Dave:

These are the 3 pics, 2 with the 1.25" fitted and not fitted. The other is the adaptor with one of my EP'S fitted as far as the collar will allow. Could you please post some pics of your diagonal with an eye piece, I want to see how far they go in, your diagonal seems to swallow them hole Dave:

I think I have just sussed why your getting forward focus, by the looks of your pics it looks like your EP'S are sitting much further inside your diagonal giving you more inward focus, is that the case Dave:

@Knighty2112 Thanks for the reply, I have spoke the dealer I usually go with about our diagonals, he says because my diagonal is dielectric it may be demanding of a slightly longer focal length. it has come from the Sky Watcher ED range of scopes and also it is a bit longer as you insert the EP, mine looks thicker than yours. So what I have done is order the same diagonal that you have, 2" Altair Astro diagonal , I am just curious as to seeing if I can get the kind of forward focus that you have. I seem to have enough even with 150x mag but would like more headroom to be safe. I have also ordered a Sky watcher 4mm UWA now that I know a 4mm is not over kill. Regards. Dave:

Knighty2112 wow so pleased you got the focuser to work with your Barlow, it would seem then that my 2.5x Barlow is to strong. I am glad you posted as I was in two minds to take an inch or so out of the back of the tube, and also I was wandering were to fit the synta finder scope shoe, glad I didn't do any cutting. So all I need then is a 2x Barlow. are there any with the brass ring compression fitting, I don't like using the screw as the securing method as I don't want to mark my EP's. By the way do all your EP'S work ok with your 2x Barlow. And also is your diagonal a Altair Astro 2" Mirror Star Diagonal. If so that might be why I cannot get focus with my 2.5 Barlow, there might be a big difference in focal length between yours and my Skywatcher 2" Di-Electric Star Diagonal. I have four EP's ranging from 24x-60x-120x-150x without using a Barlow so I think I have all the magnification covered. If I need to go in-between or stronger than 150x I would have to put my SkyWatcher Deluxe Dielectric 90 Degree Star Diagonal 1.25" to get focus. You seem to have been lucky with your choice of diagonal, fair play to you and I am pleased you got the Crayford in the end, isn't it just day and night better than the standard focuser and yes none of that greezy shizzle Regards. Dave:

It will be interesting if you're 2x Barlow will achieve focus, as you've seen from one of my pictures were I left the focuser the last time I used the scope with my 5mm eyepiece without using my Barlow. I would think for me to get focus it would require a lot more inward travel. Do you think you will need a Barlow for your ST 120? I have 120x with a 5mm and 150x with a 4mm for me thats enough without adding low contrast and blurry views with higher magnification on the ST 120. If you have quality eyepieces I wouldn't worry to much about using your Barlow. Could you let me know the outcome with a 2x Barlow, it would be great if it works. But remember you can always revert back to your 1.25" diagonal to get in focus and still have a top focuser to fine tune Dave:

Knighty2112 You are very welcome, i only wish i had a 2x Barlow to test for you. I am very pleased with it, getting that extra focus control is an absolute must when imaging or viewing the night sky. If i have to i would not hesitate in taking a bit off the back off our dear ST-120 scopes, it would be worth it, i will not count it out as something to do at a latter time Dave:

I would say there is about 3 quarters of an inch difference at the back of both focusers, the Crayford being said distance longer minus the eyepiece adapters Dave:

I have tried to line up the 2 focusers up exactly, you can see that the new Crayford is defiantly longer, that's why it wont Barlow with the 2" diagonal. I tried the Barlow with the supplied SkyWatcher 90 Degree Star Diagonal 1.25" and the 45 erecting prism And I have no problem with focus. Before i put the adapter flange on the scope I tried carefully inserting the Crayford into the tube further then it would allow with the flange and you can get all the focus you want but you would have to take a bit of the back (not an impossible job to undertake) to get the focuser further in. But like I said I can achieve all the magnification I wont without using a Barlow. I have very good Celestron X-CEL LX eyepiece's so my scope will thank me for that, and without using a Barlow I think the view is clearer and brighter. Dave

These are the exact settings I left the focuser on last night 25/3/ while viewing the moon real close up with my SkyWatcher 5mm UWA Planetary Eyepiece, without a Barlow. As you can see there is a little headroom for a closer view lets say with a 4mm Dave:

Yes it is a shame but like you said not a deal breaker. Don't forget I am using a Revelation Astro 2.5x Barlow Lens 1.25", not sure if a 2x would be better?. The smoothness of the dial is just so precise you will not be disappointed, the smaller dial is just fantastic, ultra minute adjustments. I don't no what the deal with these 2" Di-Electric Star Diagonals not getting focus it beats me. I hope if I get a real good Skywatcher 90 Diagonal 1.25" with a compression fitting I will keep focus. I don't want to use the standard diagonal as I don't want to mare my X-CEL LX eyepieces up. maybe its not a case of using a Barlow as long as you can push the scope not quite to its limits. This scope has about 240x or so at best, so I am hoping if I can stretch to a 4mm at 150x mag I would not need a Barlow. Just remember knighty 2112 if you stick with a decent 1.25" diagonal (dielectric) a Barlow will be fine. I will make some enquires unless someone here can advise. All I will say about the Crayford is its an exceptional bit of kit, I am glad I finally got one, wont be using the supplied one again that's for sure Dave: