Bintel GSO 8” F5 newt

[Startrek]

Looking at buying my second astrophotography / visual scope early next year to leave at my holiday place down the south coast
I’m considering the Bintel GSO 8” F5 newt on a Skywatcher EQ6R Mount ( currently I have a Bintel GSO 6”F6 newt on a HEQ5 mount which is working extremely well for AP and visual but this will stay in Sydney )

Q1: does anyone know if the current Bintel 8” F5 newt reaches prime focus with a DSLR without adapters, Barlow’s etc.... ? ( my 6” does no problem , no adapters etc straight into the focuser)
Q2: does anyone own the 8” f5 and are they happy with its performance mainly with AP ( I’m certain it would be a great visual scope anyway)

Appreciate any advice , experience
Cheers

[ChrisV]

I have similar - a gso 8" F5 on CGEM. I bought mine second hand here. Great for AP. And learning collimation ... I hadto fiddle the focuser a bit to get it tilted correctly. You'll need a coma corrector.

Works really well with the asi071 and before that a Canon 550d. With a baader mpcc it reaches focus fine with the 55mm spacing between sensor and coma corrector.
I'll upgrade eventually but have been happy with it for nearly two years now.

[xelasnave]

Hi Martin.
I have the 8 inch f5 GSO and think it is magic.
Many of my images here are using the eight...see my recent Orion shots ..one with the 8 inch and one with the 80mm espirt.
I added additional tube rings and a coma corrector and had no problems with focus...
After a year and many trips up North I still have not collminated the scope so it is forgiving...I will get around to that in time.
The focuser could be better but it is not bad ..mine has a bit of slop but its managable when I am not cranky.
The scope suffers one problem which isanaged with the additional rings to a degree...the tube seam is rather poor ..it is not joined and needs a strip over it with screws or solder or resin...if you tighten the tube rings it gives...I dont let it worry me as in time I plan to do a number on the tube which will see a supporr strip as mentioned, baffles and a eighth inch ply section under the focuser to reduce flex which I have not found☺.
U have yet to look at how to make the focuser better..it needs a shim or additional rollers...otherwise the adjustment is great...it moves when you tighten it down... but I have got around that...all good if not cranky and tired.
I have yet to add a baffeled dew tube but that is under construction.
The only reason I have not done the baffles is as the colmination is ok at the moment I dont want to touch it...when it gets bad I will pull it down and add baffles and focuser support.
I expect that you will be very happy with that scope...also try it without a coma corrector..I assumed it would need one but I never looked to see what coma was present...given the crop one usually must do after a stack (well that I have to do) coma may not be a problem...save the money if you can.
Alex

[Startrek]

Thanks Alex and Chris
Just what I wanted to hear , a good scope !
I was looking at the Skywatcher 8” f5 but I think the GSO dual speed focuser is much bettter, a nice solid focuser with smooth travel. The Skywatcher focusers feel a bit under engineered when it comes to supporting your accessories
Is coma on these F5 scopes a real issue for AP. For visual I don’t even notice
I will probably set the tube rings up with a longer bar so they have a wider support on the tube , say an extra 100 or 150 mm
People have suggested from 8” up they can be a windsock especially when guiding
I was out last night imaging M42 again with my 6” which is 900mm long and the wind was gusting around 20 to 25 km/hr however my guiding was running pretty good around 1.5 to 1.8 arc sec total error with RA Osc sitting around 0.32. So the wind didn’t affect the 6” to much and I’m hoping it wont have to much affect on the proposed 8” ??


Cheers

[Startrek]

Anybody else use a Bintel GSO 8” f5 newt for AP ?

Love to hear your comments

Cheers

[NorthernLight]

Hi Martin, I don’t have that particular scope but a 6” f/5. The question of coma is not whether it has it. It will. Coma is not a quality issue like astigmatism but a natural function of a curved mirror. The degree of coma (that is how much flat field without coma one gets) is determined by the f ratio. The faster the scope, the smaller the area that is free of coma. At f/5 you are not bothered much by coma visually when using ie Plössl eyepieces with their 52 deg AFOV. However, a DSLR image will show coma pretty much from the center of the image, so one can’t even crop it out. You would need a coma corrector or get used to images that look like taken at warp speed.

[Startrek]

Hi Max
Thanks for the advice
When I get my new 8” f5 scope early next year I might image initially without a CC and see if I can use my post processing to tidy up the coma
I use Startools which has a nifty module called Repair and has 3 or 4 algorithms which do a great job on eggy stars and stars with coma etc
Paying for a CC to resolve coma is not the issue, the issue is having unnecessary extra weight on the mount ( like a counter weight ) when post processing may tidy up the image.

Cheers

[Imme]

Before using the repair module try using lens module

[NorthernLight]

I use Startools as well and would be keen to learn how to get coma out of images. My 6“ has a 1.25“ focuser and i cannot find a CC for it. Eventually i want to upgrade and get a CC but meanwhile it would be nice to be able to Post process the coma out. So if you could share a workflow that would be great.

[ChrisV]

Get a coma corrector. As Max says you'll get coma through virtually the whole image without one and it will really cheese you off. I got my baader mpcc III from teleskop express. And they come up second hand on IIS every now and then.

[Startrek]

Max
Download the “Startools Manual V 1_3_5 Unofficial” PDF dated May 2014
On page 127 is “Repair” module which repairs stars affected by blooming, egg shape, coma etc...
I have only used the “Warp” algorithm in Repair which repaired all the egg shaped stars in my 47 Tucanae image.Repair has to be the last item you do otherwise it loses its affect if choose other modules to work on your Stars eg Magic
Hope this helps
Cheers
PS: I’m going to try the Lens module as well !!

###Getting back to the 8” f5 newt , looks like I do need a coma corrector then, I can afford the Televue Paracorr, how do the compare with the Baader MP CC 111 ?

[NorthernLight]

Thanks Martin, I will try it out. Regarding the Paracorr: I don’t think one can go very wrong by choosing Televue equipment.

[Startrek]

I was in Bintel on Saturday picking up some back orders and got some advice about a coma corrector for an 8” f5 newt
The Baader MPCC mk 111 is the best choice for imaging as it’s compact and light weight and does the job well
The Televue Paracorr 2 is a quality product for coma but more suited for visual use as it’s quite long and heavy

Does anyone know if I still need my 2” T ring or does the Baader CC screw straight into T ring adapter on my Canon 600D (ie: replace the T ring) and then into the focuser ??

Cheers

[spiezzy]

from memory Martin it screws into the T ring and the the MPCC goes straight in the focuser
cheers Pete

[Karlzburg]

The MPCC has M42 and M48 thread on it and it screwed straight on to my t-mount then went into the focuser.

[Startrek]

Thanks guys !

[ChrisV]

Yes what they said. MpccIII has a 2" that goes into the focuser. And has a thread on it so you can screw on a 2" uv/ir filter. T-thread on the other end goes into the dslr-t adaptor to give the correct spacing to sensor

[Startrek]

Thanks Chris
Got it

If my new 8” f5 newt wont reach focus with the baader coma corrector I could do what I did with my 6” and move the primary mirror in 3 to 5mm which gave me more “in focus” around a full turn on the focuser

There are a few ways to rectify DSLR prime focusing on newts

Cheers

[TareqPhoto]

Not Bintel or GSO, but from Meade, this is what i got from the first test only without great setup of everything


https://i.postimg.cc/dt31MTbs/Image13.jpg


Coma corrector i used is Skywatcher F4 Aplanatic, but i am sure i didn't make the backfocus perfect and i think even balancing the scope could be not proper and ofcurse collimator can be better a bit, and this image also my first time using PixInsight to stack/process LRGB, so imagine if no or very less issues how this will be, i don't think Bintel/GSO can be any less than this brand too.