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

Difference Between 90mm and 127mm or 130mm?

  • Please log in to reply
56 replies to this topic

#51 Dave96

Dave96

    Lift Off

  • -----
  • topic starter
  • Posts: 22
  • Joined: 27 Jan 2021
  • Loc: Cincinnati, Ohio USA

Posted 06 April 2021 - 02:26 PM

welcome to Cloudy Nights!

 

I think the 90mm refractor you have hits a good spot in terms of size/weight for the aperture.  Going bigger 127+ will likely require a much better mount which by itself would used your budget.

 

If you want aperture, there is substitute for a dob in terms of cost to aperture.  The 10 or 12" dobs are just an incredible value if you can adjust to the overall size.

 

What's in the middle? I think the 8" SCT is popular because it fits in between the other two.  A compact package with significant aperture.  The C8 by itself is 12lbs.  The Meade units are a couple lbs more.  This might also need a mount upgrade.

 

Have fun,

Jeff

Jeff,

You mention a SCT, which I am interested in because of the SCT's smaller size and portability. I have been researching a Celestron 6" SCT over the past few days. I know an 8" SCT would gather more light, but is more expensive of course. Does an SCT provide a good view of DSOs? Or does a SCT have a narrow FOV? I know this is a refractor forum, but wanted to get more info on a SCT since I am trying to compare to my current 90mm refractor. Thanks.  



#52 infamousnation

infamousnation

    Messenger

  • *****
  • Posts: 400
  • Joined: 10 May 2017
  • Loc: Woodstock IL

Posted 06 April 2021 - 11:28 PM

Yes



#53 infamousnation

infamousnation

    Messenger

  • *****
  • Posts: 400
  • Joined: 10 May 2017
  • Loc: Woodstock IL

Posted 06 April 2021 - 11:37 PM

How well you see a Dso is dependent on how much light a telescope gathers, more light, shows the object better.

 

A 8 inch gathers 5 times as much light as a 90mm

A 6 inch gathers 2.77 times as much light as a 90mm

 

Whether it is an sct, a newt, a mak, they all will gather light proportional to their aperture. Refractors don’t have a central obstruction, they they will gather a little more than an sct of the same size because nothing is blocking out the light

 

Its impossible for anyone to say what you will be able to see, because what you can see also depends on things like light pollution, your eyesight, and your experience.

 

So for example it’s possible for a 6 inch at a dark site to show more than an 8 inch in a city.


Edited by infamousnation, 06 April 2021 - 11:42 PM.

  • Dave96 likes this

#54 Dave96

Dave96

    Lift Off

  • -----
  • topic starter
  • Posts: 22
  • Joined: 27 Jan 2021
  • Loc: Cincinnati, Ohio USA

Posted 08 April 2021 - 08:49 AM

How well you see a Dso is dependent on how much light a telescope gathers, more light, shows the object better.

 

A 8 inch gathers 5 times as much light as a 90mm

A 6 inch gathers 2.77 times as much light as a 90mm

 

Whether it is an sct, a newt, a mak, they all will gather light proportional to their aperture. Refractors don’t have a central obstruction, they they will gather a little more than an sct of the same size because nothing is blocking out the light

 

Its impossible for anyone to say what you will be able to see, because what you can see also depends on things like light pollution, your eyesight, and your experience.

 

So for example it’s possible for a 6 inch at a dark site to show more than an 8 inch in a city.

infamousnation,

Thanks for the reply and information. I'm learning more each day about telescopes, light pollution, etc. This will help me decide which type of additional telescope to purchase.



#55 k5apl

k5apl

    Apollo

  • *****
  • Posts: 1,226
  • Joined: 19 May 2006
  • Loc: Arkansas

Posted 08 April 2021 - 09:40 AM

OP.....you have been getting some great advice here.  The refractor forum will be biased toward refractors, but other designs will give you more light gathering at less or equal cost.  My experience is that the MAKs I owned were too

restrictive with their long FL, and too fussy about thermal stabilization.  I have only looked through one portable Dob in my life that I thought had refractor-like views (it was hand-made by an amateur).  I believe that a larger scope at your

present location will not give you as good performance as a smaller scope in a dark location.  That is why I have settled on a 92mm refractor and a 130mm refractor.  The 92 is easily travelled with "locally" and is very easy to set up.  The 130mm is portable too, but the mount is larger.  Which brings us to the mount.

A pet peeve of mine is a shaky mount.  When I focus, I want no vibration.  Some mounts in the past would shake for 2or 3 seconds, or more before settling down (portable mounts).  Please consider getting a stable mount for whichever telescope you end up with.  My friend Chuck says that you can't overmount a telescope.  I use a DiscMounts DM-4 with the 92mm, and a Losmandy G11GT with the 130mm.  You don't have to go to this extreme, but you get the point.  And when I am viewing portable, I use DSCs and/or GoTo to quickly find objects of interest. I am of the camp that "comes to observe", not "acquire star-hopping skills".  YMMV.

If I was in your position, I would consider a 130mm refractor as the maximum size for now.  Its a good bump up from the 90mm you have, and its still very portable with a reasonably stable mount.  I've owned 150mm and 160mm refractors, and they required another level of work and time to meet my viewing requirements.

I don't recall you talking about budget, but I recommend by the best you can afford at this time.  I have lost a lot of money over the years buying marginal or sub-par equipment (telescopes, mounts, eyepieces).  Perhaps you can

take all of the CN advice and come up with a system that you are content with.  I wish you the best.


  • Dave96 likes this

#56 Dave96

Dave96

    Lift Off

  • -----
  • topic starter
  • Posts: 22
  • Joined: 27 Jan 2021
  • Loc: Cincinnati, Ohio USA

Posted 14 April 2021 - 11:18 AM

OP.....you have been getting some great advice here.  The refractor forum will be biased toward refractors, but other designs will give you more light gathering at less or equal cost.  My experience is that the MAKs I owned were too

restrictive with their long FL, and too fussy about thermal stabilization.  I have only looked through one portable Dob in my life that I thought had refractor-like views (it was hand-made by an amateur).  I believe that a larger scope at your

present location will not give you as good performance as a smaller scope in a dark location.  That is why I have settled on a 92mm refractor and a 130mm refractor.  The 92 is easily travelled with "locally" and is very easy to set up.  The 130mm is portable too, but the mount is larger.  Which brings us to the mount.

A pet peeve of mine is a shaky mount.  When I focus, I want no vibration.  Some mounts in the past would shake for 2or 3 seconds, or more before settling down (portable mounts).  Please consider getting a stable mount for whichever telescope you end up with.  My friend Chuck says that you can't overmount a telescope.  I use a DiscMounts DM-4 with the 92mm, and a Losmandy G11GT with the 130mm.  You don't have to go to this extreme, but you get the point.  And when I am viewing portable, I use DSCs and/or GoTo to quickly find objects of interest. I am of the camp that "comes to observe", not "acquire star-hopping skills".  YMMV.

If I was in your position, I would consider a 130mm refractor as the maximum size for now.  Its a good bump up from the 90mm you have, and its still very portable with a reasonably stable mount.  I've owned 150mm and 160mm refractors, and they required another level of work and time to meet my viewing requirements.

I don't recall you talking about budget, but I recommend by the best you can afford at this time.  I have lost a lot of money over the years buying marginal or sub-par equipment (telescopes, mounts, eyepieces).  Perhaps you can

take all of the CN advice and come up with a system that you are content with.  I wish you the best.

k5apl,

I appreciate the information. I am currently eyeing an Explore Scientific AR127 Refractor from one vendor and a sturdy mount from another vendor. The AR127 weighs about 15 pounds according to the vendor. I have never owned a reflector, SCT, MCT, or a Dob and I'm sure those would provide some great views, but the idea of collimation turns me off. Refractors seem to be more simple, easier to set up, and require much less cool-down time if any, which is important to me. I do need to get my current 90mm Refractor to a darker site, which I'm sure will show me the scope's true potential. I am still weighing the pros and cons of the different types of telescopes, plus which ones are in stock or will be available soon. Many vendors are out of stock or have long wait times. 



#57 gnowellsct

gnowellsct

    Hubble

  • *****
  • Posts: 18,345
  • Joined: 24 Jun 2009

Posted 14 April 2021 - 03:43 PM

The main thing is that if you go to a 130 mm from a 90 mm you are likely to need a better mount.

 

The 130 mm refractor is much more capable than a 90mm (I have two 92mm refractors), but mine, at least, is a good deal heavier.

 

The mechanics are important.  If you have a light duty mount like the CG5 or Super Polaris, you can put a 4" refractor on it.  That's about the limit.  OR, you can put a c8 on it and get comparable stability.  That is, the short fat ugly SCT design packs a lot of aperture into a very short lengthwise axis. 

 

I do think that a c8 or 8" Newtonian would be in order for someone who has extensive experience with the 90mm.  It is normal to want to see what aperture can do. 

 

A five inch refractor is also a good choice, but it will cost more per inch of aperture and demand more mount.  (Dobs come with their mounts) 

 

This is the refractor forum.  If you are a die hard refractor person and see no use in any other instrument design, then a 5" refractor is definitely the direction in which you should head.  It will make a noticeable difference.  If on the other hand you're curious about a larger instrument of an alternative design, they can be very cost effective.  Used C8s can sometimes be picked up for $200 to $300 (without mount).  Those tend to be older.  The new ones at $850 to $1000 are also a great value. 

 

There's no law against dual refractor observing!  Here 81mm on top of 130mm.  But it's more effective to put the apo on top of a c8, c14, etc.  Greg N

 

GT 130 and 81s Landis May 8 2018jpg.jpg

 

 

 

 


  • Mike W 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