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

Biggest Newt on HEQ5 Pro?

  • Please log in to reply
11 replies to this topic

#1 cadman342001

cadman342001

    Explorer 1

  • -----
  • topic starter
  • Posts: 69
  • Joined: 04 Mar 2017
  • Loc: Cairns, FNQ, Australia

Posted 04 August 2017 - 04:06 PM

I'd like to use an 8" but have been advised it may be / will be too much for my HEQ5 Pro mount once guidescope + dslr are added (Nikon D800)

 

What do you think / what have you got / used and got accurate guiding / long subs / good results with ?

 

What am I losing / gaining by playing it safe and getting a 6" instead.

 

Budget is absolutely fixed at $500 for the OTA only. I can get a CF 8" for that here.

 

TIA

 

Andy



#2 TimN

TimN

    Soyuz

  • *****
  • Moderators
  • Posts: 3,547
  • Joined: 20 Apr 2008
  • Loc: Ontario, Canada

Posted 04 August 2017 - 04:31 PM

I used an 8" AT8RC with an HEQ5 and a D5100 without a problem. However, the AT8RC isn't as long as an 8" newt would be and I was mounted on a pier. Unless you are a very experienced imager I wouldn't try it. Even then, the longer tube and it mounted on a tripod may be just too much. If you are just starting out I'd recommend a small refractor instead. You can get some fantastic mages and its much easier to learn on. 



#3 ChrisWhite

ChrisWhite

    Fly Me to the Moon

  • *****
  • Posts: 6,363
  • Joined: 28 Feb 2015
  • Loc: Northeast USA

Posted 04 August 2017 - 04:34 PM

Andy,

 

I'm the one who replied in your previous post about this, so might be a bit redundant but...

 

I would not go bigger than 6" on your mount.  I like f4 scopes, they are fast and despite more of a challenge to collimate than an f5, I think it is worth it for the light gathering.  If you really wanted to get something aroun 800mm focal length, you would be pretty close with an 6" f5.

 

What would you gain by sticking with a 6"?  Better guiding, longer exposures, slightly wider field of view, less impacted by wind and less frustration. 

What would you lose by not having 8"?  IMO, not much.  You lose a little bit of Focal length, but you also lose the frustration of having too big of a scope on too little of a mount.  With a DSLR you are probably going to want to take exposures in the 4 to 8 minute range with an f4, and I don't think I would be happy with the results and quality of  stars/image if I tried to do long exposure with an 8" on that mount.

 

I'm using an Atlas, which is the next size up from what you are using essentially, and with my 8" reduced (so I image at f2.8) and implementing a ultra low noise cooled CMOS camera, I don't like to push exposures past 3 minutes.  I think I could get to 5 minutes, but it would require some more tuning of my setup, and with the big surface area being sensitive to wind... I need calm air to make it all work. 

 

FWIW....

 

EDIT- I will add that with a firm budget of $500, a basic 6" scope will hold collimation and be easier to work with than a basic 8".  I think if you go for 8", carbon fiber is really a HUGE improvement over steel... but at a price.  Also, keep in mind you need a coma corrector, and this could cost another $200 to $300.  You can have a 6" steel imaging scope and Baader MPC III coma corrector for about $500 here in the states.  Not sure what you could get in Australia. 

https://www.optcorp....-telescope.html


Edited by ChrisWhite, 04 August 2017 - 04:38 PM.

  • FiremanDan likes this

#4 rmollise

rmollise

    ISS

  • *****
  • Posts: 23,273
  • Joined: 06 Jul 2007

Posted 04 August 2017 - 05:09 PM

I did this very thing during the Mars opposition of 2003 with an 8-inch f/5 Newt. It was OK for planetary imaging on a wind-free night, but I was never happy with the setup...the mount seemed just at the limit with the OTA.



#5 mikefulb

mikefulb

    Surveyor 1

  • *****
  • Posts: 1,866
  • Joined: 17 Apr 2006

Posted 04 August 2017 - 07:42 PM

No questions - 6 inches is the largest I'd recommend except for anything other than short exposures (you could do 8 for those).


Edited by mikefulb, 04 August 2017 - 07:43 PM.


#6 dkeller_nc

dkeller_nc

    Surveyor 1

  • *****
  • Posts: 1,546
  • Joined: 10 Jul 2016
  • Loc: Central NC

Posted 04 August 2017 - 08:52 PM

Since I have a D800 myself and am familiar with its size and weight, I will add to the chorus to stick with a 6", and a 6" F4 at that.  Nevermind the actual weight limit of the mount, hanging a D800 off of the end of an 8" newt on the HEQ5's lightweight tripod would give me pause.



#7 bobzeq25

bobzeq25

    ISS

  • *****
  • Posts: 23,508
  • Joined: 27 Oct 2014

Posted 05 August 2017 - 12:48 AM

Note that this isn't a yes/no situation.  It's just a question of how good or bad your guiding will be, and there a lot of factors going into that.

 

All that said, that mount is pretty much my absolute minimum for AP.  So I'll add to the chorus that 6 would be significantly better than 8.



#8 cadman342001

cadman342001

    Explorer 1

  • -----
  • topic starter
  • Posts: 69
  • Joined: 04 Mar 2017
  • Loc: Cairns, FNQ, Australia

Posted 05 August 2017 - 01:38 AM

Thanks everyone ! I will get a 6".

 

The Skywatcher Black Diamond BKP 150 OTAW Dual Speed is what I'm looking at as I notice it has the 10:1 dual speed crayford style focusser. None of the other 6 inch Newts I have seen here has that.

 

Only thing is, it's an f5 not f4 - longer FL (750 vs 600), more reach, less coma, easier to collimate but less light ?

 

Anyone know if there is an f4 equivalent ? can't seem to find one in Oz online


Edited by cadman342001, 05 August 2017 - 01:45 AM.


#9 bobzeq25

bobzeq25

    ISS

  • *****
  • Posts: 23,508
  • Joined: 27 Oct 2014

Posted 05 August 2017 - 12:44 PM

Thanks everyone ! I will get a 6".

 

The Skywatcher Black Diamond BKP 150 OTAW Dual Speed is what I'm looking at as I notice it has the 10:1 dual speed crayford style focusser. None of the other 6 inch Newts I have seen here has that.

 

Only thing is, it's an f5 not f4 - longer FL (750 vs 600), more reach, less coma, easier to collimate but less light ?

 

Anyone know if there is an f4 equivalent ? can't seem to find one in Oz online

There's this, but I'm not recommending it, not comfortable with the quality I'd expect, at that price.  F4s are more expensive to make.

 

http://www.teleskop-...il-focuser.html

 

And this, well above your budget, and I'm sure much higher quality than what you're looking at.  Quite light and stiff, good focuser, all these will pay off in the quality of your images, and in how much easier getting them will be.  This is just not a cheap hobby.

 

http://www.teleskop-...arbontubus.html

 

One thing you omitted in your summary is that the F4 will gather light faster, reducing exposure time.  And be more tolerant of guiding errors.  Not a big deal, but significant.


Edited by bobzeq25, 05 August 2017 - 12:45 PM.


#10 mikefulb

mikefulb

    Surveyor 1

  • *****
  • Posts: 1,866
  • Joined: 17 Apr 2006

Posted 05 August 2017 - 05:17 PM

You'll need a coma corrector no matter what Newtonian you chose unless you want to crop down to just the central area.

 

Depending on how picky you are the low end 6 inch f/4 scopes are serviceable and give a good value for the money.  But there will be some compromises.  You need to start researching CN and Astrobin for as many images as you can find with 6 inch scopes and contact the authors and get feedback directly from owners.

 

I think the ONTC scopes from TS are a step up but I don't think they sell anything smaller than an 8 inch for that model line.



#11 cadman342001

cadman342001

    Explorer 1

  • -----
  • topic starter
  • Posts: 69
  • Joined: 04 Mar 2017
  • Loc: Cairns, FNQ, Australia

Posted 07 August 2017 - 04:35 AM

 

Thanks everyone ! I will get a 6".

 

The Skywatcher Black Diamond BKP 150 OTAW Dual Speed is what I'm looking at as I notice it has the 10:1 dual speed crayford style focusser. None of the other 6 inch Newts I have seen here has that.

 

Only thing is, it's an f5 not f4 - longer FL (750 vs 600), more reach, less coma, easier to collimate but less light ?

 

Anyone know if there is an f4 equivalent ? can't seem to find one in Oz online

There's this, but I'm not recommending it, not comfortable with the quality I'd expect, at that price.  F4s are more expensive to make.

 

http://www.teleskop-...il-focuser.html

 

And this, well above your budget, and I'm sure much higher quality than what you're looking at.  Quite light and stiff, good focuser, all these will pay off in the quality of your images, and in how much easier getting them will be.  This is just not a cheap hobby.

 

http://www.teleskop-...arbontubus.html

 

One thing you omitted in your summary is that the F4 will gather light faster, reducing exposure time.  And be more tolerant of guiding errors.  Not a big deal, but significant.

 

 

Thanks. I'd love to be able to afford the one in the 2nd link frown.gif Shipping very reasonable though :)


Edited by cadman342001, 07 August 2017 - 04:35 AM.


#12 cadman342001

cadman342001

    Explorer 1

  • -----
  • topic starter
  • Posts: 69
  • Joined: 04 Mar 2017
  • Loc: Cairns, FNQ, Australia

Posted 07 August 2017 - 04:37 AM

You'll need a coma corrector no matter what Newtonian you chose unless you want to crop down to just the central area.

 

Depending on how picky you are the low end 6 inch f/4 scopes are serviceable and give a good value for the money.  But there will be some compromises.  You need to start researching CN and Astrobin for as many images as you can find with 6 inch scopes and contact the authors and get feedback directly from owners.

 

I think the ONTC scopes from TS are a step up but I don't think they sell anything smaller than an 8 inch for that model line.

 

Thanks




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