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

Question about adding finder

  • Please log in to reply
11 replies to this topic

#1 JustAnotherScott

JustAnotherScott

    Vostok 1

  • -----
  • topic starter
  • Posts: 181
  • Joined: 07 May 2020

Posted 13 April 2021 - 10:46 AM

Not sure if this is best section so feel free to move mods sorry

 

I just picked up a vintage University Optics 80mm. Am I crazy to think it might be a good finder for my 10" dob?

 

With  32mm eyepiece I can get 16x and 4 degrees FOV. Combined with my telrad and some higher power eyepieces I think it would be a great combo for finding harder to see stuff.

 

Only issues I can see are:

 

How would I mount it? My DOB is a sonotube.

 

Balance would be an issue too. Its already out of balance from the telrad and I only have that marginally fixed.

 

Thoughts?


  • teashea likes this

#2 spereira

spereira

    Fly Me to the Moon

  • *****
  • Moderators
  • Posts: 5,647
  • Joined: 21 Apr 2017
  • Loc: Bedford, NH

Posted 13 April 2021 - 10:50 AM

Moving to Equipment.

smp


  • JustAnotherScott likes this

#3 MellonLake

MellonLake

    Apollo

  • *****
  • Posts: 1,412
  • Joined: 16 Dec 2018
  • Loc: Toronto, Canada

Posted 13 April 2021 - 04:33 PM

I think you will run into balance issues with such a heavy telescope on a little Dob.  If you do mount it, mount it mid tube with the 80mm's centre of gravity over the trunnions.   Also the field of view is a little narrow, we are typically want more like 6°.   

 

It is a really nice complimentary telescope though.  Great for large open clusters which can be difficult in the Dob (Pleiades, Beehive, etc.) and the moon.    

 

Rob 


  • paul hart and teashea like this

#4 CarolinaBanker

CarolinaBanker

    Mariner 2

  • -----
  • Posts: 247
  • Joined: 31 Dec 2020
  • Loc: Eastern North Carolina

Posted 13 April 2021 - 04:51 PM

Could you add some weight down low to offset it? I’d probably use a lighter finder though.

#5 teashea

teashea

    Apollo

  • *****
  • Posts: 1,300
  • Joined: 20 Dec 2020
  • Loc: Lincoln, Nebraska, USA

Posted 13 April 2021 - 08:42 PM

I would also think that the tube would have difficulty holding the weight without deforming.


  • Jon Isaacs likes this

#6 JustAnotherScott

JustAnotherScott

    Vostok 1

  • -----
  • topic starter
  • Posts: 181
  • Joined: 07 May 2020

Posted 14 April 2021 - 09:21 AM

I would also think that the tube would have difficulty holding the weight without deforming.

You might be be surprised its incredibly strong.



#7 JustAnotherScott

JustAnotherScott

    Vostok 1

  • -----
  • topic starter
  • Posts: 181
  • Joined: 07 May 2020

Posted 14 April 2021 - 09:23 AM

Could you add some weight down low to offset it? I’d probably use a lighter finder though

Its tough to add weights to this set up. The mount doesn't have  a lot of room at the bottom and the tube is not ferrous.  I'm going to try a divers weight belt next time out.


Edited by JustAnotherScott, 14 April 2021 - 09:23 AM.


#8 JustAnotherScott

JustAnotherScott

    Vostok 1

  • -----
  • topic starter
  • Posts: 181
  • Joined: 07 May 2020

Posted 14 April 2021 - 09:29 AM

I think you will run into balance issues with such a heavy telescope on a little Dob.  If you do mount it, mount it mid tube with the 80mm's centre of gravity over the trunnions.   Also the field of view is a little narrow, we are typically want more like 6°.   

 

It is a really nice complimentary telescope though.  Great for large open clusters which can be difficult in the Dob (Pleiades, Beehive, etc.) and the moon.    

 

Rob 

My thinking is when combined with the telerad the 4 degrees wouldn't be an issue. I could buy a 2" eyepiece that would kick it up to around 5 degrees but they are expensive. I really want this to help me dial in on smaller objects.

 

Regarding the weight you are most like right especially with this set up. I am going to try some experiments with a divers belt counter weight system soon.

 

You were right about open clusters! I took it for a spin last night and the bee hive fit in it perfectly. It looked great!



#9 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 91,915
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 14 April 2021 - 09:34 AM

Its tough to add weights to this set up. The mount doesn't have  a lot of room at the bottom and the tube is not ferrous.  I'm going to try a divers weight belt next time out.

 

The place for counterweights is the back side of the tube at 45 degrees so the weights fit in the corner of the rocker box when pointed near the zenith. This is also a good place balance-wise since it's opposite the finder/focuser.

 

The counterweights will need to be heavier than the 80 mm, diagonal,  eyepiece and finder rings.  If I remember correctly, the Deep Space Explorers had a low altitude bearing height so you might have to use 2x-3x the added weight top side.

 

Jon


  • JustAnotherScott likes this

#10 MellonLake

MellonLake

    Apollo

  • *****
  • Posts: 1,412
  • Joined: 16 Dec 2018
  • Loc: Toronto, Canada

Posted 14 April 2021 - 09:51 AM

To Jon's point above, if your 80mm telescope weighs 8 lbs (just a guess) and you mount it at the front of the tube you will need to add 16 to 24lbs of weight to the rear of the tube (towards the front board on the rocker box).   Between the telescope and the weights you will be adding between 24lbs and 32lbs of weight to the system.  This is a lot of weight and will increase the weight of the telescope tube by more than 50%.  If you mount the telescope over the trunnions, the weight will not be as big of a factor.   

 

I really would not front mount the 80mm telescope!  Mount it over the trunnions if you do want to mount it.  It may look weird but it will work the same way.   


Edited by MellonLake, 14 April 2021 - 09:53 AM.


#11 JustAnotherScott

JustAnotherScott

    Vostok 1

  • -----
  • topic starter
  • Posts: 181
  • Joined: 07 May 2020

Posted 14 April 2021 - 10:38 AM

To Jon's point above, if your 80mm telescope weighs 8 lbs (just a guess) and you mount it at the front of the tube you will need to add 16 to 24lbs of weight to the rear of the tube (towards the front board on the rocker box).   Between the telescope and the weights you will be adding between 24lbs and 32lbs of weight to the system.  This is a lot of weight and will increase the weight of the telescope tube by more than 50%.  If you mount the telescope over the trunnions, the weight will not be as big of a factor.   

 

I really would not front mount the 80mm telescope!  Mount it over the trunnions if you do want to mount it.  It may look weird but it will work the same way.   

Its around 3.5 pounds. You're correct putting it on the end would be an issue. After using it last night I think another issue will be the length of it. Its fun to filddle with though so I'll experiment.



#12 JustAnotherScott

JustAnotherScott

    Vostok 1

  • -----
  • topic starter
  • Posts: 181
  • Joined: 07 May 2020

Posted 14 April 2021 - 10:41 AM

The place for counterweights is the back side of the tube at 45 degrees so the weights fit in the corner of the rocker box when pointed near the zenith. This is also a good place balance-wise since it's opposite the finder/focuser.

 

The counterweights will need to be heavier than the 80 mm, diagonal,  eyepiece and finder rings.  If I remember correctly, the Deep Space Explorers had a low altitude bearing height so you might have to use 2x-3x the added weight top side.

 

Jon

You're memory is correct Jon. Divers belt with weights seem to be the only thing I could use to position everything. Maybe its a completely silly idea we'll see. I could get a smaller RACI but whats the fun in that.




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