Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

A New (to me) C90

  • Please log in to reply
23 replies to this topic

#1 Tenacious

Tenacious

    Viking 1

  • *****
  • topic starter
  • Posts: 609
  • Joined: 19 Oct 2015
  • Loc: Northern KY

Posted 27 January 2019 - 05:49 PM

I have this cooling on the back deck as I type.  This is my first Mak and my first C90.   I hope to get some feel for its performance tonight. 

 

As you can see, I have bare threads where a visual back should go.  I do have a hybrid diagonal for testing.  Ultimately, I will convert it to a larger EP format.  What are the best options for 1.25" accessories?

 

DSC02174.JPG    DSC02177.JPG


  • TOM KIEHL likes this

#2 Russell Smith

Russell Smith

    Messenger

  • *****
  • Posts: 419
  • Joined: 27 Aug 2017
  • Loc: 76707

Posted 27 January 2019 - 05:55 PM

Love it.
Had the 500mm one and it was great on widefield. A bit redundant for me so I let it go.
The focus on mine was a bit rough so it did need a good cleaning and lube.
I never had to mess with optics on it.
All it wanted was a camera tripod and time outside.
  • Tenacious likes this

#3 Tenacious

Tenacious

    Viking 1

  • *****
  • topic starter
  • Posts: 609
  • Joined: 19 Oct 2015
  • Loc: Northern KY

Posted 27 January 2019 - 05:55 PM

...another one...

 

DSC02173.JPG  



#4 Tenacious

Tenacious

    Viking 1

  • *****
  • topic starter
  • Posts: 609
  • Joined: 19 Oct 2015
  • Loc: Northern KY

Posted 27 January 2019 - 05:57 PM

..one more.

 

DSC02175.JPG


  • TOM KIEHL likes this

#5 Tenacious

Tenacious

    Viking 1

  • *****
  • topic starter
  • Posts: 609
  • Joined: 19 Oct 2015
  • Loc: Northern KY

Posted 27 January 2019 - 08:41 PM

The views this afternoon were very encouraging.

 

The views tonight weren't bad, but, I think other frustrating issues are hiding much of the potential. 

 

First of all, my old Velbon camera tripod does a good job for its intended purpose.  On the other hand, it doesn't cut it as a platform for astronomical use.  Has anyone mounted a C90 on an EQ-1?  Stable enough?  As anyone might guess, I'd like this to be my travel scope, the mount will need to be small and portable, too.

 

With a focal length of 1000mm, I'm going to need a method of finding targets.  At last years ScopeOut, I picked up an aluminum-bodied red-dot finder normally mounted on firearms, I forget the brand name.  This seems like the best option, or I could always fall back to a green laser pointer.  It would be easy to make a GLP adapter for the empty finder bracket.

 

It's cold out tonight, below freezing.  Trying to twist the focuser puts a lot of force on the tripod and the target gets lost.  I'm sure the focuser is lubed with that syrup stuff popular with scope importers.

 

Finally, I wasn't out there for long, but I suspect the collimation is a bit off.

 

So far, I think this will work out great after some effort is put in.



#6 grif 678

grif 678

    Apollo

  • *****
  • Posts: 1308
  • Joined: 22 Dec 2010
  • Loc: NC

Posted 27 January 2019 - 09:46 PM

You can take off the base plate, there is a screw under the plate that keeps the front tube from coming all the way off when focusing. Remove that screw, screw the front tube off. Then take a small brush and clean all the old grease out of the threads, then regrease with the Mobil red synthetic grease, it does not take much, and the focuser will smooth out and there will not be any play. Make sure you hold the tube so that the old grease falls away from the mirror, and not into it. After you put the new grease on, you can screw the tube back on, but before you put the restraining screw back in, screw the tube back off, and take a rag and remove the excess grease that was forced out of the threads, this will keep excess grease from getting on the lens. Remember, it only takes a small amount, and I do not put any at the end close to the mirror, it will work down that way when you screw the tube back on.


  • Kasmos and Tenacious like this

#7 astro140

astro140

    Mariner 2

  • -----
  • Posts: 273
  • Joined: 28 Jan 2008
  • Loc: Mayhill, New Mexico

Posted 28 January 2019 - 11:41 AM

I have this cooling on the back deck as I type.  This is my first Mak and my first C90.   I hope to get some feel for its performance tonight. 

 

As you can see, I have bare threads where a visual back should go.  I do have a hybrid diagonal for testing.  Ultimately, I will convert it to a larger EP format.  What are the best options for 1.25" accessories?

 

attachicon.gif DSC02174.JPG   attachicon.gif DSC02177.JPG

Celestron used to make an accessory called the Large Accessory Ring (LAR) which screwed to the outside treads of the C90 (LAR occasionally come up on e-bay) .  That coupled with a Celestron 1 1/4 visual back allowed you to use 1 1/4 accessories.  I have read that at some point Celestron changed the pitch of their treading so all visual backs may not fit.  My visual back is an older one.

Attached Thumbnails

  • LAR.jpg
  • LARvisualback.jpg

  • Tenacious likes this

#8 wfj

wfj

    Surveyor 1

  • *****
  • Posts: 1628
  • Joined: 10 Jan 2008
  • Loc: California, Santa Cruz County

Posted 28 January 2019 - 06:10 PM

I prefer the C90 visual back.

 

vb-c90.jpg



#9 Tenacious

Tenacious

    Viking 1

  • *****
  • topic starter
  • Posts: 609
  • Joined: 19 Oct 2015
  • Loc: Northern KY

Posted 29 January 2019 - 12:16 AM

Thanks for the kind replies Russel, Billy, Astro140, and wfj.

 

I definitely intend to replace the syrup lube.  The Mobil red synthetic grease looks good to me. 

 

My biggest reason for wanting to adapt the C90 to 1.25" EPs is because I don't want to start another collection of 0.965" format.  I found this thread from 10 years ago by Memento.  He thoroughly wrestled with the C90 issues, including collimation.  It's an interesting read.   The information contributed there has convinced me that I might as well stick with my hybrid diagonal.   His modified Skywatcher 1.25" diagonal (post #54) looks tempting, too.

 

At Wfj, where is that VB available?



#10 wfj

wfj

    Surveyor 1

  • *****
  • Posts: 1628
  • Joined: 10 Jan 2008
  • Loc: California, Santa Cruz County

Posted 29 January 2019 - 12:47 AM

https://www.telescop...ope-models.html


Edited by wfj, 29 January 2019 - 12:52 AM.

  • Tenacious likes this

#11 Apophis Dude

Apophis Dude

    Lift Off

  • -----
  • Posts: 2
  • Joined: 02 Jun 2017

Posted 02 February 2019 - 05:49 AM

I use the Celestron Visual Back-1 (93653-A), My LAR is made by Orion (07158)

1.25 JP.jpg

 


  • Tenacious likes this

#12 houndsbourgh

houndsbourgh

    Sputnik

  • *****
  • Posts: 30
  • Joined: 26 Dec 2017
  • Loc: Hailey, Idaho

Posted 02 February 2019 - 03:36 PM

Couple other readily available solutions for a Visual back on the C90. Meade 07036 back cell adapter. About $19.00 on Amazon this one has the minimalist approach. No knurled shoulder for ease in removal or install. Pin spanner is the best tool. Once installed if your OTA set screw is long enough you never need to remove it to use the original accessories. Second is the Baader SCT/T2 Universal Adapter fo ETX. This is a 2” SCT solution. Sells for about $35.00. Looks similar to the original LAR and has a install and removal ring built in. In the Baader product description it actually lists the C90 as one of its applications. You may need to remove you OTA set screw as it does have some relief machined into the back. Last but not least we have a CN member that makes 3D printed LAR clones and dust covers. Very nice stuff. But he just had an addition to his family so hobby stuff is on hold. I will throw his ID up when he is back in action. With his permission, of course.

Edited by houndsbourgh, 02 February 2019 - 03:48 PM.

  • Tenacious likes this

#13 houndsbourgh

houndsbourgh

    Sputnik

  • *****
  • Posts: 30
  • Joined: 26 Dec 2017
  • Loc: Hailey, Idaho

Posted 04 February 2019 - 11:09 AM

Yet another option from the Meade ETX family. The 07210 No.93 45-Degree Erecting Image Prism is a direct fit diagonal. No adapter needed. I come across several comments of a good fit with the older C90 OTA. No comments on reflectivity on this one. But it provides a very elegant solution for 1.25" eyepieces. Sells for about $39.00 on Amazon.


  • Tenacious likes this

#14 Geo.

Geo.

    Vendor - Nexstar Parts

  • *****
  • Vendors
  • Posts: 4929
  • Joined: 01 Oct 2008
  • Loc: Upstate NY

Posted 05 February 2019 - 10:04 AM

ETX accessories may fit or not. The threads are different. If they fit they were probably machined on a Monday. My homemade solution is turning old tele-extenders into visual backs. The female tele-extender thread fits the C90's rear port thread. I cut it down and fit a 1.25 eyepiece holder to the female thread end of the tele-extender. The eyepiece holder has a compression ring.

 

C90_VB_2.JPG

 

It's hard for a C90 to hold collimation without the support of fresh (like fresh in the last decade) grease.

 

 


  • terraclarke and Tenacious like this

#15 houndsbourgh

houndsbourgh

    Sputnik

  • *****
  • Posts: 30
  • Joined: 26 Dec 2017
  • Loc: Hailey, Idaho

Posted 09 February 2019 - 12:14 PM

I must have a Monday adapter. The threading on my Ceslestron T-Adapter has more slop in it than my ETX accessory ring. I was considering modding a T-Adapter to make the C90 Visual back. But as I looked at the ID OD requirements for the lock ring I saw a problem. Well not a problem but an anomaly. The interior shoulder required for the .965 to 1.25 transition removes over a 1/4 turn of back focus. My C90 Mak Telescope with the Celestron LAR and Visual back installed has about 1/4 of turn left of back focus. Not a lot if you consider the variable requirement of eyepiece and diagonal combinations. So I chucked my visual back up in the lath and zipped the treading off. Gained a 1/4 turn right there. Still another 10mm available to be removed if you consider a long 1.25 drop in. Like a Celestron zoom eyepiece. That still leaves 3mm before it touched the back of the OTA. The extra 10mm will add another 1/4 turn of available back focus. Geo's solution for eyepieces is a bit more elegant. But carrying the 1.25 size fit as close as possible to the back OTA increases flexibility for diagonal and eyepiece combinations.

Attached Thumbnails

  • IMG_20190209_40860.jpg

Edited by houndsbourgh, 09 February 2019 - 01:06 PM.

  • terraclarke and Tenacious like this

#16 Tenacious

Tenacious

    Viking 1

  • *****
  • topic starter
  • Posts: 609
  • Joined: 19 Oct 2015
  • Loc: Northern KY

Posted 09 February 2019 - 08:14 PM

..... But carrying the 1.25 size fit as close as possible to the back OTA increases flexibility for diagonal and eyepiece combinations.

That was my take-away from Memento's thread that I referenced in post #9.   After handling the scope and seeing the ID of the baffle, the hybrid diagonal makes a lot of sense to me.

 

I'm equally curious about how folks have been mounting C90s over the years.  In this case, it seems portability is as important as stability and smooth control....



#17 houndsbourgh

houndsbourgh

    Sputnik

  • *****
  • Posts: 30
  • Joined: 26 Dec 2017
  • Loc: Hailey, Idaho

Posted 09 February 2019 - 11:08 PM

Oops went a little to far. Off on my measurements cutting the visual back down. Optimal cut was right down the center of the set screw holes. I decided to face them off for looks. Everything but the zoom fits. Fell short a good 2-3mm. Looks like my measurements came off the recessed shoulder not the end of the OTA. Ack! I have some round stock on hand and have decided just to make the thing from scratch. As far as a mount goes I have been using a Kenko head on a Manfrotto tripod for years. It has an adapter for camera or Vixen style mounts. Most of the time I direct mount my C90. But if an actual camera is attached to the scope a short Vixen style bar helps balance everything. With the high power and narrow field of view in this little scope I like something with gear driven adjustments.

Attached Thumbnails

  • image.jpeg
  • image.jpeg

  • terraclarke likes this

#18 Tenacious

Tenacious

    Viking 1

  • *****
  • topic starter
  • Posts: 609
  • Joined: 19 Oct 2015
  • Loc: Northern KY

Posted 10 February 2019 - 10:39 AM

Wow, interesting solution for the VB.   If you make those from scratch, are you thinking of selling some?

 

Your C90 looks great on that mount. 



#19 houndsbourgh

houndsbourgh

    Sputnik

  • *****
  • Posts: 30
  • Joined: 26 Dec 2017
  • Loc: Hailey, Idaho

Posted 10 February 2019 - 12:26 PM

Depends on the fab time. I do not have a CNC rig. Making a complete solution could be costly. Lock rings are a real time suck. I have made LAR clones in the past but they are raw in finish and a real time suck as well. Currently I have some parts being printed in ABS. I think that may be the way to go for a cost effective visual back. The density of ABS is good for a moderately loaded LAR or Visual Back. Any eyepiece or diagonal would be fine. Pile of extensions and a camera I would worry a little. A sag or misalignment may develop over time. Encountering shear forces high enough for a failure even then would most likely total the scope. I will let you know.



#20 houndsbourgh

houndsbourgh

    Sputnik

  • *****
  • Posts: 30
  • Joined: 26 Dec 2017
  • Loc: Hailey, Idaho

Posted 17 February 2019 - 11:45 AM

Update on the 3D printed parts. All I can say is baelyn did an excellent job. Threads are nice and sharp and fit just like the alloy accessories.  Prices were very reasonable. I had a LAR,  LAR dust cover and shroud cover made in grey ABS.  Colors are what he has on hand. I also requested a LAR with a offset. The offset LAR will have the end OTA flush with the LAR face. Looks like an elegant way to move the visual back up to 8mm closer to the OTA. Much easier than cutting up accessories. The stock set screw will need to be set aside when it is in place. I will post that one when he gets it to me. 

Attached Thumbnails

  • IMG_20190217_37128.jpg
  • IMG_20190217_25668.jpg

  • terraclarke, Kasmos and Tenacious like this

#21 houndsbourgh

houndsbourgh

    Sputnik

  • *****
  • Posts: 30
  • Joined: 26 Dec 2017
  • Loc: Hailey, Idaho

Posted 17 February 2019 - 11:57 AM

Picture of the LAR installed. Offset version will have the end of the OTA even with the face of the LAR.

Attached Thumbnails

  • IMG_20190217_9359.jpg

  • TerryWood, terraclarke, Kasmos and 1 other like this

#22 Tenacious

Tenacious

    Viking 1

  • *****
  • topic starter
  • Posts: 609
  • Joined: 19 Oct 2015
  • Loc: Northern KY

Posted 17 February 2019 - 02:46 PM

Those look great!  Excellent job.



#23 houndsbourgh

houndsbourgh

    Sputnik

  • *****
  • Posts: 30
  • Joined: 26 Dec 2017
  • Loc: Hailey, Idaho

Posted 18 February 2019 - 07:57 PM

Playing with offset solutions on the LAR still.  Here is the modified Meade LAR. I ran it through my rotating stage on my mill.  Results were a nice sleek adapter with .5mm offset. No knurled ring for install/removal though.

Attached Thumbnails

  • IMG_20190218_5785.jpg
  • IMG_20190218_15449.jpg

  • Tenacious likes this

#24 houndsbourgh

houndsbourgh

    Sputnik

  • *****
  • Posts: 30
  • Joined: 26 Dec 2017
  • Loc: Hailey, Idaho

Posted 18 February 2019 - 08:09 PM

Next up one of baelyns LARs.  I ran this through my mill as well.  Using specifications we have been discussing.  His version will be quite a bit more refined than this. Just a prototype LAR far as is am concerned. I did decide to remove the threads of the Visual Back.  Moves the 1.25" forward by quite a margin.  I can't see myself using the threads anyway

Attached Thumbnails

  • IMG_20190218_3288.jpg
  • IMG_20190218_23690.jpg
  • IMG_20190218_58171.jpg

  • Tenacious likes this


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics