Go Back   IceInSpace > Beginners Start Here > Beginners Equipment Discussions

Reply
 
Thread Tools Rate Thread
  #1  
Old 09-07-2019, 11:40 PM
RussellH
Registered User

RussellH is offline
 
Join Date: Oct 2005
Location: Sunny Queensland
Posts: 158
Bintel vs Skywatcher f5 6” newts

So Bintel have Skywatcher 6” f5 newt listed as an Astrograph, but not the GSO version of the same scope.

Skywatcher https://www.bintel.com.au/product/sk...v=6cc98ba2045f
Bintel https://www.bintel.com.au/product/bi...v=6cc98ba2045f

So what are the differences that make one for AP and the other for visual? The description just talks about a small secondary mirror. Is that it.

Also, does anyone have an opinion on the Skywatcher for AP?

Thanks. Russell.
Reply With Quote
  #2  
Old 09-07-2019, 11:55 PM
Startrek (Martin)
Registered User

Startrek is offline
 
Join Date: Dec 2017
Location: Sydney
Posts: 1,240
Russell
Done my homework over a 6 month period on the Skywatcher 6” and 8” f5 scopes vs the Bintel GSO 6” and 8” f5 and f6 scopes for both visual and astrophotography

They both get the job done in their price category but I find the GSO focusers superior and the general build a bit better quality ( finish , hardware used , paintwork etc) Also the secondary and primary mirrors have better adjustment in the GSO

GSO use BK7 glass for their mirrors
Skywatcher use Pyrex which is a little more expensive
Personally I can’t see any difference

I have a Skywatcher 12” Goto Dob which is an excellent instrument for the money. Only reason why I bought a Skywatcher is that GSO don’t make a 12” Goto dob

I think from memory the Skywatcher 6” and 8” are slightly heavier than the GSO

I went GSO for my astrophotography rigs and Skywatcher for my big visual rig

Very happy with my decision

My 2 cents ....

Martin
Reply With Quote
  #3  
Old 10-07-2019, 12:13 AM
raymo
Registered User

raymo is offline
 
Join Date: Sep 2011
Location: margaret river, western australia
Posts: 4,905
All SW Newts have sufficient back focus for AP, some GSO Newts do and
some don't, so maybe the listed 6" f/5 doesn't.
raymo
Reply With Quote
  #4  
Old 10-07-2019, 12:37 AM
Startrek (Martin)
Registered User

Startrek is offline
 
Join Date: Dec 2017
Location: Sydney
Posts: 1,240
All the GSO 6” and 8” newts reach focus
When I bought mine I asked Don from Bintel to fit some 3mm cork spacers to bring the primary mirror into the OTA a bit
A 3mm packer or spacer gives you more travel on your focuser
It’s just a tweek I requested and it’s great especially for planetary and lunar focusing on live view with your Barlow’s or Powermates etc...
Reply With Quote
  #5  
Old 10-07-2019, 05:34 AM
RussellH
Registered User

RussellH is offline
 
Join Date: Oct 2005
Location: Sunny Queensland
Posts: 158
Thanks guys.

This may be my lack of understanding, but I don’t know why they just don’t build them all with more back focus these days, and throw in an e tension tube to use if needed to keep the eyepieces at the correct distance. Is there an option to just fit low-profile focusers to increase back focus?

I think all astronomy retailers need to overhaul their shops. With Atrophotograohy being so accessible these days, i think every scope and affected accessory should state their backfocus distances. Also a side issue but every item should state their mounted weight, so the impact on loading up your mount can be calculated, since there are so many extras you can throw on these days.

Last edited by RussellH; 10-07-2019 at 09:11 AM.
Reply With Quote
  #6  
Old 10-07-2019, 07:46 AM
RussellH
Registered User

RussellH is offline
 
Join Date: Oct 2005
Location: Sunny Queensland
Posts: 158
I as just looking at coma correctors if I wanted to try an f5 instead of f6, and may have found a solution to both several problems at once.

Bintel Coma Corrector
https://www.bintel.com.au/product/bi...v=6cc98ba2045f
GSO Coma Corrector
https://agenaastro.com/gso-2-coma-corrector.html

This coma corrector has a back focus requirement of 75 - 80mm. So shouldn’t this mean no matter whether you throw it on an AP classed, or visual classed scope, it’ll provide plenty of back focus distance? At least for Canon Camera’s, with a standard back plane at 55mm, there should be room to spare. From what I’ve found so far, without any extra attachments, it’ll need a 15 or 20mm spacer to reach back focus.

So what am I missing here? If a coma corrector is recommended anyway (maybe not for an f6, but it can’t hurt) what’s bad about doing this, and why wouldn’t it be a universal solution to the question of whether there’s enough back focus or not on a particular scope?

The two main concerns I can think of is possible vignetting down the long focus path (easily corrected in post editing) and the extra long tube length throwing off mount balance and being slightly less stable mechanically and possible visually.

There must be a big gotcha - what am I missing?
Reply With Quote
  #7  
Old 10-07-2019, 09:13 AM
Startrek (Martin)
Registered User

Startrek is offline
 
Join Date: Dec 2017
Location: Sydney
Posts: 1,240
You will need a coma corrector for both f5 and f6 newts
Remember you are looking at a $300 or $400 telescope ( budget low end ) not a $2000 or $3000 newt
I’ve tried the Bintel GSO coma corrector for AP and it doesn’t cut it , only for visual
The tried and tested coma corrector around the world for years is the Badder MCCP mk3
Fits straight into my Canon 600D then into the focuser not other adapters needed
Mines works perfectly to the edge of field in both scopes
There not cheap but a small investment for ongoing long term results, you get nice round clean stars
Once again I did my homework !!
A coma corrector won’t fix your back focus
Have the spacers fitted to the primary and your off and running
Cheers
Reply With Quote
  #8  
Old 10-07-2019, 09:28 AM
RussellH
Registered User

RussellH is offline
 
Join Date: Oct 2005
Location: Sunny Queensland
Posts: 158
As you say, $300 telescope. Adding a $330 coma corrector just seems wrong But of course it’s transferrable to any upgrades I make, just kind of hard when starting as all the extras are turning out to be triple the price of the scope itself.

Is a 3mm spacer enough to cope if you starting adding extras such as an oag though? Or does. 3mm spacer give you more than 3mm back focus distance? I’m concerned somewhere down the track it’ll hit that back focus wall again.

I’m also still trying to see if I can fit an 8” onto the HEQ5. I know 10kg is the recommended max. I’ve got what I think are all of the extras and the f5 8” total at about 10.5kg at the moment.

If it wasn’t for all the recommendations against it, the f4 would come in at about 10kg. Apparently somewhere once there was even a carbon fibre version, which would have weighed even less, but it seems to be not available currently.
Reply With Quote
  #9  
Old 10-07-2019, 10:33 AM
Startrek (Martin)
Registered User

Startrek is offline
 
Join Date: Dec 2017
Location: Sydney
Posts: 1,240
The 8” f5 is to big and heavy for the HEQ5 particularly if you intend to do long exposure AP ( 3 to 10 minute subs ) If you are only going to do short exposures up to 1 minute then the 8” f5 should be OK. If you are buying a second hand HEQ5 then it will be more subject to periodic error so with more weight you just multiply the problem so guiding will struggle a bit , plus add poor seeing conditions and frustration looms
The 8” is more prone to wind than the smaller scope that’s why you would need the bigger mount EQ6-R
Don’t underestimate the 6” f6 it’s a great scope
I bought the 8” f5 to chase after galaxies amongst everything else down at my dark location
3 to 4mm spacers or packers will give you an extra 2 to 3 turns of your focuser , plenty
Here’s some of my images taken this year with the 6” F6 and HEQ5 mount

All the best !!
Attached Thumbnails
Click for full-size image (64BF1373-D700-4B83-B153-56777EBC440C.jpg)
202.7 KB18 views
Click for full-size image (4FBDDEE0-070D-4014-AEA1-00D1E8EA0EFE.jpg)
212.9 KB21 views
Click for full-size image (F7D3A29F-AE9D-421D-BEEA-41028C739F15.jpg)
219.4 KB16 views
Click for full-size image (E329CE2D-079A-4786-AF1E-64AB8C1E0DF5.jpeg)
108.9 KB17 views
Click for full-size image (BEBB728E-6C7A-4226-87EF-55257300DF9E.jpeg)
76.1 KB20 views
Click for full-size image (718F3BFB-21B3-4C36-B022-22C60B36E3A7.jpeg)
45.4 KB25 views
Click for full-size image (D93E63BF-F43A-44B4-B026-628437F4BE01.jpeg)
166.6 KB23 views
Reply With Quote
  #10  
Old 10-07-2019, 10:50 AM
RussellH
Registered User

RussellH is offline
 
Join Date: Oct 2005
Location: Sunny Queensland
Posts: 158
I know Martin, if it wasn’t for needing it customised, I probably wouldn’t still be debating, given I’m now committed to a coma corrector wither way. The 6” f5 would be nicer if it wasn’t for the focal length drop. Going from 900mm to 750mm seems a lot on paper, although when I put it into the FoV calculator at Astronomy Tools, it doesn’t look that much different. Plus the 900mm barely covers the main Orion Nebula cloud whereas the 750 surrounds it nicely, so that is a bonus.

The depressing part of the FoV calculator is looking at the planets with these specs, they’re just tiny points of light, so I guess there’s no escaping a 2nd scope for Planetary imaging. I haven’t been game to look into the requirements for that, as I know the $$$ signs will scare me away, but I know the temptation will keep gnawing in the back of my mind.

*edit* a thought. How badly does a barlow affect imaging quality? Maybe a 2x barlow on the f5 would satisfy me on some of the smaller NSO’s for now?

Last edited by RussellH; 10-07-2019 at 10:53 AM. Reason: Barlow question
Reply With Quote
  #11  
Old 10-07-2019, 11:22 AM
tileys
Registered User

tileys is offline
 
Join Date: Nov 2007
Location: NW Sydney, Australia
Posts: 86
A benefit you will get with the Skywatcher over the GSO - at least for the time being - is that the newish ASI autofocusser is apparently compatible with the Skywatcher focusser but not the GSO one...
Reply With Quote
  #12  
Old 10-07-2019, 11:25 AM
RussellH
Registered User

RussellH is offline
 
Join Date: Oct 2005
Location: Sunny Queensland
Posts: 158
Quote:
Originally Posted by tileys View Post
A benefit you will get with the Skywatcher over the GSO - at least for the time being - is that the newish ASI autofocusser is apparently compatible with the Skywatcher focusser but not the GSO one...
Oh really? Well that puts a fly in the ointment. While the autofocusser is on my list, it is a “if manual doesn’t work” thing down the track. I am uograding to a 10:1 focusser though, so not sure if that makes a difference. Can you point me to where you found out this information?
Reply With Quote
  #13  
Old 10-07-2019, 11:28 AM
Startrek (Martin)
Registered User

Startrek is offline
 
Join Date: Dec 2017
Location: Sydney
Posts: 1,240
I dont use the astronomy tool calculator because my 6” f6 can easily fit the Orion Nebula and lagoon nebula in FOV with room to spare
On paper it shouldn’t but in reality no issue at all
My DSLR crop sensor frames nearly all objects in the sky except for Eta Carinae ( about 75% ) and the running chicken ( about 50 %) but these are huge objects
Don’t always trust these calc tools with templates , to me they are only a guide

Cheers
Reply With Quote
  #14  
Old 10-07-2019, 11:37 AM
Startrek (Martin)
Registered User

Startrek is offline
 
Join Date: Dec 2017
Location: Sydney
Posts: 1,240
I use a Televue 4 x powermate and 5 x powermate to image planets
Get my focal ration up to around f25
The Canon 600D on 5 x zoom get you close to 1:1 pixel resolution
This combo works well but ultimately seeing conditions governs the quality of your planetary images
Reply With Quote
  #15  
Old 10-07-2019, 11:39 AM
RussellH
Registered User

RussellH is offline
 
Join Date: Oct 2005
Location: Sunny Queensland
Posts: 158
Looking at the product details for the ASI focuser, it looks like the compatibility part is the mounting bracket. That shouldn’t be a big issue to overcome as I could probably design one that works on my 3D printer.

So the FoV tool is a bit out, fair enough, I’m still leaning towards the f5 at the moment, as I think I can get it with the 10:1 focuser for the same price as the f6 without.

As for the barlow, good to hear it can be done (not sure I can afford Powermate prices though). Even if not imaging, I need something to impress the wife to justify the money I’m spending, and there’s nothing like seeing the rings of Saturn to impress people.
Reply With Quote
  #16  
Old 10-07-2019, 11:50 AM
tileys
Registered User

tileys is offline
 
Join Date: Nov 2007
Location: NW Sydney, Australia
Posts: 86
Yes - I think it's just the mechanical linkage so a homeprinted bracket could put the focusser in the correct alignment with the GSO focusser I imagine - I have an f/4 with the 10:1 GSO focusser - I would be keen on getting the focusser as I'm not happy with my focus regime - too much manual fiddling
Reply With Quote
  #17  
Old 10-07-2019, 11:54 AM
RussellH
Registered User

RussellH is offline
 
Join Date: Oct 2005
Location: Sunny Queensland
Posts: 158
Yeah when I was investigating the F4 versions, it seems focussing is the only drawback people have issues with, but it’s a big issue. With the focuser and software to automate it, that would seem to nullify the f4 arguments, unless there’s more problems with them that I haven’t come across yet. Of course that assumes the software does a good job too.

Now if only they could get software and hardware to automate collimation of RC scopes, I’d be in nirvana with a wide newt and a long RC
Reply With Quote
  #18  
Old 10-07-2019, 01:03 PM
RussellH
Registered User

RussellH is offline
 
Join Date: Oct 2005
Location: Sunny Queensland
Posts: 158
Bummer, the focuser listing was a mistake so no saving on the 6” f5
Reply With Quote
  #19  
Old 10-07-2019, 04:43 PM
ausastronomer (John Bambury)
Registered User

ausastronomer is offline
 
Join Date: Mar 2005
Location: Shoalhaven Heads, NSW
Posts: 2,459
Quote:
Originally Posted by RussellH View Post
Thanks guys.

This may be my lack of understanding, but I don’t know why they just don’t build them all with more back focus these days
Hi Russell,

It isn't a problem with some telescope designs, but it is with newtonians. The more back focus you have, the larger the secondary mirror required to fully illuminate the required field size. For visual astronomy you want to minimise the size of the secondary mirror, as a larger secondary mirror causes slight degradation in image quality. For astrophotography the size of the secondary mirror does not matter.

Cheers,
John B
Reply With Quote
  #20  
Old 10-07-2019, 04:55 PM
RussellH
Registered User

RussellH is offline
 
Join Date: Oct 2005
Location: Sunny Queensland
Posts: 158
Ahh right. That explains the descriptions talking about the secondary size. Thanks for the explanation.

I’m back looking at the 8” f5 again. I should be able to keep weight around 10.5kg if all the manufacturer specs are right. I know the concern is image stability with any movement, but my scope will basically be ina static position and I can possibly build a shelter. An 8” ends up same price as the 6” with an focuser upgrade.
Reply With Quote
Reply

Bookmarks

Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +10. The time is now 09:57 PM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Advertisement
OzScopes Authorised Dealer
Advertisement
SkyWatcher Australia
Advertisement
Lunatico Astronomical
Advertisement
Celestron Australia
Advertisement
Bintel
Advertisement
Meade Australia
Advertisement
NexDome Observatories
Advertisement
Astronomy and Electronics Centre
Advertisement