127ED focuser

[telemarker]

Having just got the SXV-AO unit running on the 127ED, I found that this setup could be used OK with a OSC camera. However, when it comes to using the AO with with my ST-8300 mono camera and filter wheel I run out of in-focus on the 127ED. After doing my allowance on a lodestar before Xmas, I need a cheap fix for this - the Moonlite will have to wait.

I have the advanced focuser for astrophotography, so... am I able to remove the Red collar used for attaching the finder and/or the black spacer next to the red collar, or are these critical for focuser function/attachment?

Anyone overcome a similar lack of in-focus problem without resorting to a Moonlite etc... or cutting some length off the tube. :eyepop:

[wasyoungonce]

I wrote a pdf on this problem (in the files section of the ED127 yahoo forum (http://tech.groups.yahoo.com/group/ed127/), or see attached) as I could measure the old focuser and new advanced focuser differences. This is mainly because of the extra ring spacer added to the flange of the draw-tube neck (see pdf).

The Advanced focuser adds 24mm length to the optical train. This was a complete stuff up on NG's part. You probably already know this though.:(

The factory fix is to shorten the OTA tube at the flange end. Since the OTA end looks like a rolled thread...and the flange end has a small undercut land...this may not be easy for us folk. Attached is a pic of the OTA tube flange thread.

The way the new rear flange draw-tube neck is designed...with raised threads will also make trimming this neck down and re-threading almost impossible. Sorry I do not have a pic of the new flange neck and thread to show what I mean.

I think the Explore scientific scopes stated that the drawtube neck housing was pressed into the flange. I cannot see any signs of this but if it is then maybe it can be pressed out and machined down and or pressed inwards. But as I said I have not seen any indication the flange/draw-tube neck housing is pressed/glued in (this may have been on the original rear flanges, not the flanges made for the new focuser's, see attached pic of original old flange).

I am getting some spacers for my FL reducer for this scope and may also run out of inwards focus travel.

If I do..I'll have to suck it up and get a Moonlite.

There are many others in this same situation...we are all "stumped" apart from something like a Moonnlite or Feathertouch option.

Keep this discussion going. I would love to hear from others on this!

[telemarker]

Thanks Brendan,
You inspired me to take mine apart. As I see it the only way would be to shorten the flange tube under the finder rotator area and put a on new thread to screw on the focuser collar right at the base of the flange - no more finder support. I don't have access to a workshop but I might be able to get someone at work to have a look at it.

Regards
Keith

[wasyoungonce]

Isn't this thread "raised". If it is..this would be difficult. Sorry I haven't had mine apart for awhile and I somehow misplaced the old pics of this neck and thread...maybe...can you posite a piccie?:D

Once machine work starts to get around $250..then a Moonlite is looking good.

[telemarker]

Brendan,
The threads are not raised on my flange tube (see second picture). My thought is to shorten this to something like the first image (badly photoshopped proposed shortened flange tube) and attach the finder somewhere else. Your thoughts?

[wasyoungonce]

Hi Keith...Ha you had me going...I thought your flange neck unscrewed..but it's photoshop'd....had me going!:lol:..I should learn to read more...:doh:

What you are suggesting would work. From what I saw of Alfred's CF version of this scope, they moved the finder to the OTA tube and obviously shortened the flange neck. They used the same Advanced focuser.

I was thinking the threads were raised a lot..they are raised but this is a small amount. There is a smll undercut land behind them but if you lathe cut into the neck obviously this is not an issue as you will lets say cut away around 25mm (1").

So worst case you cut out 25mm, then, you may need an extension tube for some instances. Not a big problem.

As I measured,, the Advanced focuser adds 24mm to the image train! The only thing to be careful is that the focuser full racked in doesn't vignette the light path.

I have attached a pic of Alfred's CF 127ED.

So what you are saying should work..wanna do mine as well;)?

So hey, what do you other owners of 127's think? Come on don't be frightened to post!:shrug:

[Brundah1]

If I may but in - hello Brendan - I am part way towards the infocus solution.
So far I decided to move the finderscope (SV F50M) to midway along the OTA and offset to the left 45 deg. I use my NEQ6 at minimum height and find mounting the finder in the OEM position a PITA. The mid OTA point remains roughly the same height and if your finder is a RACI its a breeze to use.

Now to the next step, the above mod removes the need for the collar, so either shortening the focuser mounting tube or shortening the OTA is a viable option.

Either option runs the risk of constricting the light path at full infocus. But do you need to remove the full 24mm from the Adv Focuser light path? Perhaps Alfred could be enticed to provide some visual observing dimensions on his CF version? Perhaps 20mm may be enough for most visual observing and would still remove the cutback in the existing OTA threaded area.

From Brendan's accurate measurements (24mm) between both types of focusers, I tend to favor shortening the OTA.

Another option if machining becomes too expensive in OZ is to get Moonlite to machine a custom made adaptor flange to eliminate the lack of infocus and also include an improved focuser mounting collar.

David

[wasyoungonce]

Hi David.

Alfred is not responding at the moment. I think shortening the tube and cutting new threads is a good idea but I think not many people (and machine shops) will have the equipment to do this.

In fact either method will work ok.

Just harping back about the draw tube possibly vignetting the light path (if the focuser is moved fwd)....hmm maybe not as the older focuser was already 24mm further inwards. So it should be ok?:shrug:

edit:
Just putting in some more pics from Alfreds CF OTA and focuser and a test of his 5D Mk11 full frame camera with a 1.25" and 2" T ring adaptor.

As you can see the 1.25" vignettes and the 2" ..just a little...which is probably because of the full frame not focuser draw tube.

[Brundah1]

Thanks Brendan,

Another option, perhaps out of left field is the Baader 3" Steel Track focuser:
http://www.teleskop-express.de/shop/product_info.php/language/en/info/p766_Baader-STEELTRACK---3--Crayford-focuser---short-design.html
Export price AUD 372!

Telescope Service lists many accessories for full frame cameras that work with this focuser including full frame radial guider 9mm thick and a 2.5" flattener providing full frame coverage.

As before Moonlite offer a custom flange service (although their price USD100 is if you buy their focuser, I'm sure other arrangements could be made). So a new flange could be made to suit Baader 3" back focus without altering the 127ED OTA tube.

So this could be an option for those considering upgrading to a used Canon
5D MkII, these have been on Ebay for under AUD 1800.

Yes some lateral thinking can always brings up other interesting engineering solutions.

David

[wasyoungonce]

Well at the moment, for me, I have enough in-focus travel so as they say..don't fix something that doesn't need fixing.

I've spent like no tomorrow on other bright shiny things lately so this is a "maybe later issue for me".

That said....I suspect one day I'll have to deal with this issue. Or, I could throw on my older focuser which doesn't have this extra spacer ring and in-focus issue.

[Brundah1]

Brendan, are you saying you have enough in focus for visual? Does that also include using a 2" diagonal?

For me I would also like to have unrestricted visual observing capability with my TV EPs and Powermates :)

That said, a major upgrade such as a Baader 3" or Moonlite would need to be "prioritised" against "other expenditure" ;)

[wasyoungonce]

Hi David.

I rarely do visual...I mean who'd look thru a scope;).....except for drift align :D...with a skywatcher 12.5mm reticule and a 1.25" diagonal. I have enough in focus rake for this with a little to spare.

I also had the same with my 450D and TV .8X FL reducer but I didn't space it correctly so I haven't re-tested this yet.

As others have said..in most cases the lack of in-focus rake is not a problem for most doing Astrophotography ..until they start adding a combination of filter-wheels/AO units/FL reducers and or OAGs.

[wasyoungonce]

Remember I said I would not muck around with my focuser unless I needed to..well I need to. I am a dill.:( But I suspected I may run into this!

I've spaced my TV .8X reducer correctly (according to the book) and I cannot reach in-focus travel enough to focus stars...just misses by mere mm.

So it's either modify my focuser or a Moonlite. Couldn't afford a Feathertouch and to be honest a Moonlite is pushing the envelope as well.

[wasyoungonce]

Well I looked at the older std focuser...it won't cut the mustard. No focuser lock and it slips too easily.

I'm seriously considering a Moonlite for following (just thinking out loud here) :
If I modify my Advanced focuser flange I still need a solution for moving the finder. This means a new finder mount and some engineering;
Modifying the flange will cost $ as well;
Moonlite option might be 1/2 ~ 2/3 $ more than all the above (I'll need a new finder mount as well) but this is reasonably attractive.

I am looking at a std Tri-knob Moonlite with focuser lock...maybe upgrading this later to a motorfocus (I know I have to send it back for this.)

Does anyone know if Moonlite will custom make adaptors like for their 2.5: drawtube to lets say my TV .8x reducer (2.4" threaded, don't exactly know the threads)?

Anyone with a Moonlite on their 127ED?

[Visionoz]

Brendan

I'm sure the MoonLite LF refractor focuser comes with 2 finder fittings - mine has and I ordered mine to be the LF one (with a custom flange that cost $60 extra to suit a BD120ED because the original MoonLite focuser for the BD120ED is a 2" model). Ron's happy always to make you the customer happy - email him and he'll let you know for sure what he can do

HTH
Cheers
Bill

[wasyoungonce]

Hi Bill.

Thanks..I'll do that. I wanted to ask about 2.5" Drawtube to other adaptors as well apart from the std 2.5" to 2". Would be nice to screw my FL reducer straight to a 2.5" adaptor than go to a 2.5" to 2" nose piece reducer.

[wasyoungonce]

Ok Ron at Moonlite can do custom work...aka make a 2.5" to TV reducer adaptor for $80.

They will do custom work for Moonlite focuser owners, not if you are not an owner.....I do not believe they will make a custom flange unless you are already an owner.

So its looking like a Moonlite Large format crayford is the way go.

Ron was very helpful...so its decision time.

[telemarker]

I dropped the flange in to the workshop yesterday. Just waiting for a text to pickup, then time to test. :D

[wasyoungonce]

Hi Keith. Well done. Do update us on this.

I'm probably going the Moonlite way..depends..on moon and planets and wallet all coming into alignment.

I envisaged that I would put on a Moonlite/FT one day..so ..it looks as if this day has arrived ..if not earlier than expected.



edit:

Moonlite order is "done"! They are also making a custom 2.5" adaptor for my reducer.

[telemarker]

Finally had a chance to test the shortened flange. Absolutely no problems achieving focus managed a whole 2 frames before I had to pack up. So far looks good with no further vignetting problems. Now for some clear skies.

Regards
Keith

[wasyoungonce]

That's excellent Keith. How much did you get taken off?

As you know I've gone the ML CFL with DC motor way. It is in transit was we speak. Also got a 2.5" to TV FL reducer made.

Ron Newman was very helpful.

I'll post back when it arrives.

[telemarker]

Merciless t'was I. Took it right down as per the mockup pic. If I need to add anything further I can. No room for the finder ring. The finder arm can be screwed to the tube ring (I use a RA finder) so no big problem.

The moonlite solution was just too expensive for me but it looks an attractive and functional fix. Motorised is the way to go too. Computer focussing? What controller will you use?

Regards
Keith

[wasyoungonce]

Hi Keith.. To be honest...the ML is too expensive for me as well. Bread and point for the family meals for the next few weeks;).

ML use and supply a Rigel Systems battery operated, multi speed controller with their DC motors. The motor is supposed to be able to lift 18lbs with the CFL focuser. Which is supposed to be as much as the steppers but the steppers have holding coil current so ....we shall see.

I am eyeing off a an astrogene1000 dual focus controller (http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/4331423/page/1/view/collapsed/sb/5/o/all/fpart/1) interface. It uses PWM motor controls to drive DC motors and has full ASCOM and autofocus capabilities. I believe it will work with my ML handset as Gene (of AstroGene) makes the Rigel SYS controllers.

[wasyoungonce]

Keith, I meant to ask .."are you a member of the ED127 yahoo forum (http://tech.groups.yahoo.com/group/ed127/)"?

If you are do you mind posting up pics or a pdf description of the mod you did to the focuser.

I suspect many others would be interested in this and it may benefit them.:D

[telemarker]

Yes, I'm a member of that forum. I'll see if I can get some pics this weekend and put something together.

Regards
Keith

[wasyoungonce]

Thanks Keith.

That would be great and very helpful to others.:thumbsup:

Brendan

[telemarker]

Brendan,
Could you peruse/comment on this.

Regards
Keith

[wasyoungonce]

That's just the ticket Keith. Many others will be able to see what you have done when facing the in-focus issue.

My ML is still...."in transit"...sigh!

I must say...."Bozzie" looks more loyal than my "Mozzie".... who won't stay outside with me on cold nights!:shrug:

[wasyoungonce]

ML CFL has arrived.

Works a treat. No problems lifting camera and reducer. Had a small Anodising imperfection on the side of the focuser body..meh!..could have happened during shipping and too small to worry about.

You can focus with the left had knob but this moves all the DC motor gear train and is less than practical to use. It's really not designed for this in any case.

The DC controller works very nicely. It appears to be able to resolve into small enough steps for AP, but only just. By this I mean you can probably be 5 or so steps either side of focus and find it's acceptable but the steppers could resolve to around 100+ steps either side..more accurate. The DC controller has a RJ11 jack for hook-up to the Rigel sys GCUSBnFocus interface (http://www.astrogene1000.com/products/gcusb_nfocus/gcusb_nfocus.htm), so you can temp control autofocus via computer.

I'll be getting this interface..only around $50USD.

I got a 2.5" custom adaptor made for my TV reducer so to fit it straight into the Drawtube. I'm glad I did, makes it very easy to use. I'm having trouble getting the spacing right for the TV 0.8x reducer/flattener..but that's another story.

Everything is nicely made although I'm confused about the finder scope dovetails. I suspect they are vixen size but they have quite small footprints. I have ordered a stellervue finder scope mount for my old finder but I suspect the finder foot may only half fit into the ML finder dovetails?

So..over all it's great but as with every new equipment..you need to rush out to buy accessories to make it all work!

Anyone else with a ML have issues with the finder dovetails?:shrug:

edit:
Forgot to mention. I needed a 2" extension tube to reach prime focus with my DSLR (this is normal). I reached in-focus with my TV .8x reducer/flattener no problems with plenty of in-focus travel still left. So they have spaced this focuser and flange correctly!