RASA 11

[Miguel1983]

Hi,

i received my rasa yesterday and i’ve been fiddling with it.

one thing that troubles me is the retaining ring on the front lens group.

It is a very loose fit and it seems to be very hard to fasten it properly with the camera adaptor.

any suggestions ?

 

 

 

[symmetal]

Congratulations on getting a RASA 11 🤗

Are you saying you can't screw it on any tighter than you have it. It should keep screwing on until the inside edge of the retaining ring meets the lens group front surface, so I'm not sure why you can't screw it on any tighter.

Note that the inside edge of the retaining ring has a surface at 45 degrees or so to the lens assembly front surface.  When you drop the M48 adapter inside the retaining ring its edge should be free to move up and down over the over the 45 degree surface until the retaining ring is screwed onto the front lens group, when the adapter edge will sit flush against the lens group with the retaining ring holding it firmly. The 45 degree surface allows the m48 adapter to move left,right,up and down while being tightened, and end up coaxial with the lens assembly rather than possibly having it sit slightly off centre when tightened which may be the case if there was no 45 degree angled surface to ride on.

When new the edge of the M48 adapter may be too sharp, where instead of riding around over the 45 degree surface it digs in and jams causing it to end up tilted when screwed onto the lens assembly. It can then have some wobble in the adapter until it unjams and sits correctly. Mine initially did this and I just ran a piece of fine emery paper around the edge of the M48 adapter to remove the sharp edge and allow it to move freely which fixed it.

Alan

[Miguel1983]

16 hours ago, symmetal said:

Congratulations on getting a RASA 11 🤗

Are you saying you can't screw it on any tighter than you have it. It should keep screwing on until the inside edge of the retaining ring meets the lens group front surface, so I'm not sure why you can't screw it on any tighter.

Note that the inside edge of the retaining ring has a surface at 45 degrees or so to the lens assembly front surface.  When you drop the M48 adapter inside the retaining ring its edge should be free to move up and down over the over the 45 degree surface until the retaining ring is screwed onto the front lens group, when the adapter edge will sit flush against the lens group with the retaining ring holding it firmly. The 45 degree surface allows the m48 adapter to move left,right,up and down while being tightened, and end up coaxial with the lens assembly rather than possibly having it sit slightly off centre when tightened which may be the case if there was no 45 degree angled surface to ride on.

When new the edge of the M48 adapter may be too sharp, where instead of riding around over the 45 degree surface it digs in and jams causing it to end up tilted when screwed onto the lens assembly. It can then have some wobble in the adapter until it unjams and sits correctly. Mine initially did this and I just ran a piece of fine emery paper around the edge of the M48 adapter to remove the sharp edge and allow it to move freely which fixed it.

Alan

Thanks Alan,

yes I've seen that the knurled retaining ring has a sloped surface to centre the camera adapter.

A same slope on the camera adapter would be a better design.

But what troubles me more is the amount of play the retaining ring has on the treads of the lens cell.

It can actually skip treads when tension builds up and the camera adaptor is not perfectly centre.

 

[symmetal]

Ah! I'm with you now. Yes that's certainly not right. Mine was fairly stiff to turn when new but freed up after a few tries. Is it a new RASA 11 or a previously used one? If new contact your seller who should sort it out. If used do the threads look well worn. A replacement locking ring may help. Hope you can get it sorted quickly.

Alan

[Miguel1983]

1 hour ago, symmetal said:

Ah! I'm with you now. Yes that's certainly not right. Mine was fairly stiff to turn when new but freed up after a few tries. Is it a new RASA 11 or a previously used one? If new contact your seller who should sort it out. If used do the threads look well worn. A replacement locking ring may help. Hope you can get it sorted quickly.

Alan

Alan,

it is brand new, maybe a design change from Celestron to add some more play in the ring ? Maybe some users had binding problems ?

You can see how much play I have in the attached video from my first post.

I do have to say when all is well centered it does lock up well and the ring doesn't move anymore.

I have the UFC system incoming so I'll see how I do with that adaptor.

Maybe a 3D printed shim can help, we'll see.

 

[symmetal]

As long as it's secure when done up properly is the main thing. Hope it fits well with the UFC plate. I noticed on your video that the ring holding the clear filter in the front of the lens group is protruding beyond the front face. On mine it's slightly recessed when done up. I have the UFC system too. The vignetting is rather severe using the stock M48 adapter, particularly with a full frame camera and the UFC system is much better. The Baader adapter plate isn't conical like the M48 adapter so sits flat against the front face. The protruding ring may fit inside the opening on the Baader plate though as I had to make a conical insert as mentioned below I'm not sure.. There also looks like a flexible, possibly anti-reflective insert sitting inside this ring too which wasn't on my RASA. 

If using the UFC system with external filters you'll want to remove this clear filter anyway. I found quite noticeable relections and coloured spectral flares from bright stars outside the camera FOV when using the UFC system. The Cloudy Nights forum has many posts about this issue and seems to be reflections from the edges of the lenses in the lens assembly which are not visible using the M48 adapter as they are blocked by the vignetting.

Removing the clear filter from its mounting ring and fitting the mounting ring back in place helped as it obscures the edges of the lenses to some degree, but to fix it properly I 3D printed a tube with a conical front end which sits snugly inside the UFC aperture from just before the UFC filter holder up to the front edge of the removed clear filter holder. I then sprayed the inside of this tube with one of the rather expensive 'super' black paints. The tube has 0.8mm thick walls so is rather fragile but when fitted in place shouldn't need handling very often. This fixed the issue for most images, though a bright star on the edge of the scopes 52mm imaging circle may still cause some issues.

You will probably have some tilt issues unless you're very lucky, due to the extremely narrow depth of focus, and the UFC tilt adapter is worth getting, though it is rather expensive for what it is. Much easier to adjust compared to the camera front tilt plate though.

Don't rotate the camera to frame the shot either or you will almost certainly introduce some new tilt. Align the sensor long edge parallel to the RA movement direction and leave it there. If the framing isn't what you want just do a mosaic of two panels. At f2.2 it doesn't take long to complete a panel even with narrowband. 🙂

Good luck.

Alan

[Miguel1983]

6 minutes ago, symmetal said:

As long as it's secure when done up properly is the main thing. Hope it fits well with the UFC plate. I noticed on your video that the ring holding the clear filter in the front of the lens group is protruding beyond the front face. On mine it's slightly recessed when done up. I have the UFC system too. The vignetting is rather severe using the stock M48 adapter, particularly with a full frame camera and the UFC system is much better. The Baader adapter plate isn't conical like the M48 adapter so sits flat against the front face. The protruding ring may fit inside the opening on the Baader plate though as I had to make a conical insert as mentioned below I'm not sure.. There also looks like a flexible, possibly anti-reflective insert sitting inside this ring too which wasn't on my RASA. 

If using the UFC system with external filters you'll want to remove this clear filter anyway. I found quite noticeable relections and coloured spectral flares from bright stars outside the camera FOV when using the UFC system. The Cloudy Nights forum has many posts about this issue and seems to be reflections from the edges of the lenses in the lens assembly which are not visible using the M48 adapter as they are blocked by the vignetting.

Removing the clear filter from its mounting ring and fitting the mounting ring back in place helped as it obscures the edges of the lenses to some degree, but to fix it properly I 3D printed a tube with a conical front end which sits snugly inside the UFC aperture from just before the UFC filter holder up to the front edge of the removed clear filter holder. I then sprayed the inside of this tube with one of the rather expensive 'super' black paints. The tube has 0.8mm thick walls so is rather fragile but when fitted in place shouldn't need handling very often. This fixed the issue for most images, though a bright star on the edge of the scopes 52mm imaging circle may still cause some issues.

You will probably have some tilt issues unless you're very lucky, due to the extremely narrow depth of focus, and the UFC tilt adapter is worth getting, though it is rather expensive for what it is. Much easier to adjust compared to the camera front tilt plate though.

Don't rotate the camera to frame the shot either or you will almost certainly introduce some new tilt. Align the sensor long edge parallel to the RA movement direction and leave it there. If the framing isn't what you want just do a mosaic of two panels. At f2.2 it doesn't take long to complete a panel even with narrowband. 🙂

Good luck.

Alan

Alan,

thanks again for the reply.

The protruding element you noticed isn't the clear glas filter, it is al felt covered 3D printers ring to cover up the treads inside the cell, the clear glas filter is already removed.

I have done my research a bit and saw that there are possible reflection coming from those treads.

the 3D printed ring is just not pushed back all the way in the video, it's flush in normal circumstances.

I have ordered the full set UFC pieces, so the 42mm camera adapter (Omegon Cam) , slider base, 2" filter slider, tilter, variable (15-20mm) adjustment ring and 2 x 5mm spacers and the telescope adaptor UFC 70.

 

Just printed a cable router too, but waiting until UFC pieces get here to finish up.

 

It's a fat scope, even on a GM2000

I ran a pointing model yesterday, and I've got to say, Celestron most have done a good job redesigning the mirror support/focusing mechanism on the V2, I've got a very good pointing RMS.

The model was comparable to that of my Esprit 120.

IMG_6822.HEIC IMG_6825.HEIC

[symmetal]

You look to be familiar with the RASA and its design features, so much of what I said you probably knew. 😊

The UFC pieces you ordered are the same as I have, apart from also having an M54 camera adapter for the ASI6200MM. I also have the Celestron dew heater ring, though with the heat given off by the camera when cooled, it may not be necessary.

The 3D printed tube insert I made does cover those threads on the clear filter mounting. The inside surfaces of the UFC sections are also not that dark, so I made the tube to slide inside it, which holds it nicely in position. 

Yes, the mirror support on the V2 is very stable. I was concerned that a meridian flip might cause it to flop a little but there is no change in focus after a flip. One corner has very slightly different star shapes after a flip but not enough to noticeably affect the image when stacked.

One thing I recommend is not to let it fall when lifting it onto the mount like me. 😭 Luckily the only damage was the corrector plate and the guide scope, which took the initial hit. All fixed now.

Alan

[Miguel1983]

Oh my god, the horror 😱.

i have been thinking on a tube for the UFC system too, we’ll see if it’s necessary. 

[Miguel1983]

Some updates:

The Baader UFC components arrived today

Installed a mini PC and PPBa on the scope (needed to print some new mounting accessories).

With a personalized touch

Installed the curved ring to minimise star diffraction.

With my pier in the lowest position I'm almost touching the ceiling, just checked that because that's my flats position with my Geoptik flat panel, so I'll need to tilt the scope a bit hoping the dew shield is up to the load.

 

[symmetal]

Looking good Miguel. 😃

Not sure if your dew band will have much effect that far back, but it may not need to. 😉 I 3D printed my dew shield and made it shorter than normal to avoid it hitting the shed roof . What's the weight of your counterweights? Mine's on an EQ8-R and it has three 10kg weights further down the shaft than yours are. Also where's your guide scope going to fit?

Alan

[Miguel1983]

On 03/10/2023 at 18:41, symmetal said:

Looking good Miguel. 😃

Not sure if your dew band will have much effect that far back, but it may not need to. 😉 I 3D printed my dew shield and made it shorter than normal to avoid it hitting the shed roof . What's the weight of your counterweights? Mine's on an EQ8-R and it has three 10kg weights further down the shaft than yours are. Also where's your guide scope going to fit?

Alan

I was planning on 3D printing a dewshield, but it just a little bit to big to print in one piece. 
I have 2 12kg weights on there.

No guider needed —> 10micron mount.

Miguel

[symmetal]

37 minutes ago, Miguel1983 said:

No guider needed —> 10micron mount.

Oops. Silly me. 

Alan

[Miguel1983]

Little update on the RASA 11.

Last week the weather was OK enough to finish tuning the scope and shooting some testshots.

This is a 31x30s stack of M31

Worked on tilt for hours using Hocus Focus in NINA looking at the numbers after each run, but in the end I just took looping exposures and tuned it on the fly looking at the stars, this went faster then using Hocus Focus.

Iy's not perfect yet, but I think we can agree it's pretty close.

And this is a 60x60s stack of NGC281 RGB (Omegon 571C + CLS CCD)

[symmetal]

That's looking very good. Tilt looks well corrected. Luckily the Baader tilt corrector makes it fairly easy to adjust. I aligned mine such that the 3 tilt adjusters are at 12, 4 and 8 o'clock with respect to the sensor and adjustments are fairly predictable if you remember the RASA image flips left and right. 🙂

You don't seem to have any noticeable coloured flares around the edge either, so maybe you won't need to add an internal black tube. It's dependant on where the brighter stars outside the FOV are positioned of course, and on mine M101 and M51 showed significant flares before adding the tube.

I should think you're well pleased. 😊

Alan

[Miguel1983]

9 minutes ago, symmetal said:

That's looking very good. Tilt looks well corrected. Luckily the Baader tilt corrector makes it fairly easy to adjust. I aligned mine such that the 3 tilt adjusters are at 12, 4 and 8 o'clock with respect to the sensor and adjustments are fairly predictable if you remember the RASA image flips left and right. 🙂

You don't seem to have any noticeable coloured flares around the edge either, so maybe you won't need to add an internal black tube. It's dependant on where the brighter stars outside the FOV are positioned of course, and on mine M101 and M51 showed significant flares before adding the tube.

I should think you're well pleased. 😊

Alan

Thanks !

that's a good tip aligning the tilt-plate on the sensor, didn't think of that 😶.

Miguel

Edited October 11, 2023 by Miguel1983

[ollypenrice]

This is looking really good.

Olly