Jump to content

Goodbye elongated stars, hello smile!!

swag72

By swag72
in Imaging - Discussion

Recommended Posts

swag72

swag72

Posted
Posted

Well, it's been a troublesome couple of days, I broke my collimator (trying to collimate it!!), I can't get my DSLR to fit on the reducer anymore and just everything conspired against me.

Well at last, with the help of CCD inspector (sort of!) and about 1-2mm of packing with cut up pieces of tablet plastic, I have at last got myself some round stars!! We had to pack the space in between the SW flange and the Moonlite focuser with 1-2mm - So the flange is out of square by that much.

I will be contacting FLO on Monday and get them to order me a new flange, as well as keep an eye out for some small pieces of sheet metal or something. Don't know how long the pieces of tablet plastic will hold for.

So finally, after not wanting to look at my scope ever again, I'm happy. I'll post an image in the morning to show you the ridiculous-ness of it all.

Thanks to you for helping me try to fathom the problem as well as offering helpful advice to sort it. This is what SGL is all about :)

Link to comment
Share on other sites
  • Replies 27
  • Created
  • Last Reply
Spikey

Spikey

Posted
Posted

I've been following your various threads with interest Sara, glad you got to the bottom of the problems and have got a temporary fix in place. You've certainly had your fair share of niggles.

Link to comment
Share on other sites
steppenwolf

steppenwolf

Posted
Posted

I'm surprised that you are buying a new flange, Sara - these are turned on a lathe so I would expect them to be true - I'd be more suspicious of the optical tube itself. In any event, I am delighted that you have resolved the issue or at least found the discrepancy in the light path.

Link to comment
Share on other sites
swag72

swag72

Posted
  • Author
Posted

@Olly and Steve - How would be the best way to test this?

Are you suggesting that the end of the OTA may not be sitting true? The issue I have with the flange is that the screw holes on it and the Moonlite don't quite marry up, and so when you tighten the screws to hold the focuser in place it actually pushes the Moonlite upwatds and off of the base of the flange. We have filed the holes on the flange to try to marry them up better with the focuser screws, but I think I need to look at a more permanent fix than some tablet plastic!

Link to comment
Share on other sites
swag72

swag72

Posted
  • Author
Posted

I really don't want to fiddle with the collimation of the focuser especially as with it being rotatable, I will be in a right pickle if I move it!!

I'm not in disagreement with you Nadeem about Skywatcher QC - Would welcome thoughts on how to try a more permanent fix.

Link to comment
Share on other sites
swag72

swag72

Posted
  • Author
Posted

Here's some images I've just taken. I have marked the gap in one that I had to make in order to make it acceptable for me as well as how things are mounted.

I would like to be able to put this to bed now once and for all, but if as has been suggested it's the OTA, then I can't see how that's do-able.

I shall watch this with interest.

post-18339-133877741464_thumb.jpg

post-18339-133877741471_thumb.jpg

post-18339-133877741485_thumb.jpg

post-18339-133877741492_thumb.jpg

post-18339-133877741498_thumb.jpg

post-18339-133877741505_thumb.jpg

Link to comment
Share on other sites
swag72

swag72

Posted
  • Author
Posted

Yes, but do I need a flange or am I using the wrong size Moonlite? Your pictures show the Moonlite screwing direct into your OTA - Mine screws into a flange that screws into the OTA.

As you can see from the picture, there is no way the Moonlite will screw direct into the OTA as the flange acts as a step down ring.

Mmm, curious - How come I've ended up with the wrong size Moonlite for my scope......

Link to comment
Share on other sites
Nadeem Shah

Nadeem Shah

Posted
Posted

For your reference Sara, I have the 'Synta Regular 3 Bolt' fitting as described from the link below from the moonlite page (near the bottom of page). Which is supposed to fit the DS Pro Refractors 80,100 & 120 with a flange size of 96mm.

MoonLite Telescope Accessories

The choice is yours if you want to get a bigger flange from Moonlite to fit onto your scope.

If it was me, I would put the original focuser back on, then at least I know it will be square on back of the ota....

Nadeem.

Link to comment
Share on other sites
swag72

swag72

Posted
  • Author
Posted

If it was me, I would put the original focuser back on, then at least I know it will be square on back of the ota....

What and not bother with the Moonlite? What will putting the old focuser on show? Everything sits square between the focuser, flange and OTA ........ Until, I come to screwing it all together - That's when the issues start. THe Moonlite is then pushed upwards by the flange screws.

Link to comment
Share on other sites
Merlin66

Merlin66

Posted
Posted

Sarah,

OK.

Here's what to do.....

Note the position of your current"spacers".

Re-set the moonlight focuser square to the white flange and make sure it's tight and square.

Then undo the three large Philip head screws which holds the flange to the tube and re-insert your spacers between the edge of the flange and the OTA.

This should give a similar "tilt" to the one you found good for the moonlight.

This would/ could / should have been obvious when a colllimated laser was placed into the focuser - it would have shown the beam off centre. Alll you've done is tilt the focuser to bring the "virtual" spot back on centre.

If all this works/ goes to plan then look at ways and means of locking the flange to the OTA - filing the rear edge of the OTA to re-compensate for the wedges; additional tapped holes screws to better hold the flange......

Just my 0.02euro

Link to comment
Share on other sites
ollypenrice

ollypenrice

Posted
Posted

Ken has a point above.

On the other hand Nadeem's system is far better than yours in which there are too many bits all with the potential to be misaligned. I don't think FLO necessarily sold you the 'wrong' Moonlite but just one which retains the SW flange. If you can get rid of that and have an all-Moonlite attachment like Nadeem's then I'd go for that.

Olly

As I said somewhere along the line and as Ken is saying above, I think, there is nothing to be gained by aiming a laser form an off axis focuser at the middle of the objective. The axis of the focuser will still not be the same axis as that of the light cone from the lens.

Link to comment
Share on other sites
Peter Drew

Peter Drew

Posted
Posted

Sara. If, as you say, the flange screws into the SW main tube, what are the three cap head screws doing?. From your description it seems to me that these screws are causing the problem by tilting the focuser base when tightened. :)

Link to comment
Share on other sites
swag72

swag72

Posted
  • Author
Posted

Thanks all - I think I'll drop FLO a line. I get what you are saying Ken, but I really don't want to be filing the OTA or drilling extra holes.

@Peter - Sorry not sure I know what screws you mean. From the OTA there are philips head scresw that hold the flange in place. Then on the flange are raised hex screws that then hold the Moonlite in place. These hex scres between the flange and Moonlite are the problem ones.

Link to comment
Share on other sites
FLO

FLO

Posted
Posted

I have just responded to Sara's enquiry after speaking with Ron at Moonlite but seeing this thread I think it might help to post it here too:

Hi Sara,

I have spoken with Ron who has confirmed my own thoughts. You do have the correct flange for your telescope and you are attaching it via the correct holes (the Skywatcher-120 has a larger diamater OTA so uses a step-down flange so look's different to the setup shown in Nadeem's photos).

We think the Skywatcher flange is not screwed on square to the telescope tube. The solution is to remove the shims then fit the Moonlite so it sits neat and tidy. Then loosen slightly the three cross-head screws that fix the white Skywatcher flange to the telescope tube. Then with a laser in the focuser and a paper lens-cap (with centre marked) fitted to the front of the telescope, grip the focuser and adjust the focuser position until the laser spot is centred on the the paper cap's centre-mark. Then tighten the three screws. The focuser will then be centred on the optical axis.

It is highly unlikely the Moonlite focuser or flange are not square as they are tested using CCD Calc during manufacture.

Please try the above, if successful it will be a lot more elegant than using shims. If you need a replacemant Skywatcher flange please let me know.

Hope that helps.

Regards,

Steve

Let us know how you get on Sara :)

Steve

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

Go to topic listing

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.