Grab and go scope for Night Vision

[Trentend]

Recently picked up a used Skywatcher Mak127 as a grab and go scope for lunar and planets (so far so good although the small FOV is a little frustrating and, being a reflector man am not used to the new viewing position even when seated - will try rotating the diagonal next time so I can view with a straight back/neck to make it more dob-like..). 
Anyway, will this be any good for afocal viewing with my OVNI-B NV goggles? Thought I’d read somewhere that NV works better with fast scopes (the Mak is very slow) but I may have just made that up. Loving the NV views through the big dob but portable it ain’t.

[Highburymark]

It should be good for globulars if you don’t have too much light pollution. But its very slow focal ratio isn’t ideal for night vision - you want fast optics to suck in as much light as possible. My main NV scope is F/3.3 for that reason. However, slower scopes can work very well if skies are reasonably dark and you target brighter objects like M13, M92, M3 and M5.

[PeterW]

Moderate speed refractor and the 55mm Plossl afocal (now with a 67mm extra adapter). I use an 80mm f4 jumbo finder with a little extra reduction prime focus, handheld, so you can swing it about to find stuff. Play with field of view calculators so you can get an estimate Of what you’ll see. Focal length sets the field of view, speed the brightness. small scopes are good for viewing the big stuff, the opposite of your big dob.

 

peter

[Trentend]

Thanks Peter, slightly off topic but I did consider a frac for a grab and go purely for lunar and planets (not thinking about the NV) but was put off assuming I wouldn’t get enough magnification due to the short focal lengths. I tried an ED72 for a while a few years ago which had a very wide field of view but I could never get close up to the moon/Jupiter having been used to doing that in an 8” F5 reflector. Even with 8mm “planetary” eyepieces in the binoviewer and high power on the powerswitch the views were small. I know I could go mono with barlows etc but I’m wedded to using both eyes. Not sure if I could also put a Barlow in front of the Binotron (which has an OCS45) in a frac or would the views be mush with all of that glass and light loss. 

I’m still drawn more to lightweight reflector like the VX6L F8 but I don’t want cooling to be a problem (more a grab, wait and go on high powers) which brings me back to a portable frac!!

 

[GavStar]

For Grab and go night vision use my preference is a fast petzval flatfield refractor. What sort of budget were you thinking of?

Edited November 1, 2020 by GavStar

[Deadlake]

22 hours ago, GavStar said:

For Grab and go night vision use my preference is a fast petzval flatfield refractor. What sort of budget were you thinking of?

You mention petzval flat field refractor. Is it the flat field part that is important, so would adding a flat field adapter and reducer work just as well? When you mention petzval I think Tak FSQ or Televue --> Ouch in the wallet. What about a Takahashi Epsilon?

Edited November 2, 2020 by Deadlake

[PeterW]

It’s all a case of what focal length you want and the speed you can get to. Flat field and fast is good as is 2”’focusser so you can use the Televue 67mm plossl afocal unit to speed things up good and proper. 
 

peter

[GavStar]

2 hours ago, Deadlake said:

You mention petzval flat field refractor. Is it the flat field part that is important, so would adding a flat field adapter and reducer work just as well? When you mention petzval I think Tak FSQ or Televue --> Ouch in the wallet. What about a Takahashi Epsilon?

Two reasons, Petzvals are typically faster than other refractors which is important for nv and also I find when using the 67mm afocally having a flatfield gives better stars at the edge (you are often really pushing these long focal length eyepieces at these speeds).

Yes I have a Takahashi fsq85 and fsq130 and they are both brilliant with nv but pricey as you say. There are other petzals eg by Sharpstar or askar that are significantly cheaper and would work well I think.
https://www.365astronomy.com/askar-fra400-f-5.6-quintuplet-astrograph-apo-apochromatic-refractor-telescope.html

https://www.teleskop-express.de/shop/product_info.php/info/p11518_TS-Optics-121SDQ-Apo-121-mm-f-5-6-Quintuplet-Flatfield-Apo.html

 

I did have a Takahashi Epsilon 130d and it’s a nice scope for visual nv work but didn’t give the crispness of the fsqs. Once I got the fsq85, the epsilon’s days were numbered.

 

 

Edited November 2, 2020 by GavStar

[Deadlake]

9 hours ago, GavStar said:

Two reasons, Petzvals are typically faster than other refractors which is important for nv and also I find when using the 67mm afocally having a flatfield gives better stars at the edge (you are often really pushing these long focal length eyepieces at these speeds).

Yes I have a Takahashi fsq85 and fsq130 and they are both brilliant with nv but pricey as you say. There are other petzals eg by Sharpstar or askar that are significantly cheaper and would work well I think.
https://www.365astronomy.com/askar-fra400-f-5.6-quintuplet-astrograph-apo-apochromatic-refractor-telescope.html

https://www.teleskop-express.de/shop/product_info.php/info/p11518_TS-Optics-121SDQ-Apo-121-mm-f-5-6-Quintuplet-Flatfield-Apo.html

 

I did have a Takahashi Epsilon 130d and it’s a nice scope for visual nv work but didn’t give the crispness of the fsqs. Once I got the fsq85, the epsilon’s days were numbered.

 

 

F 5.6 with a flat field corrector? I was thinking of a TOA-130 with a reducer+flatterner for NV work and then I could attach an extender-Q for visual/planetary. Or is this trying to get too much utility out of one scope and best to go with separate telescopes. Also how much does the imaging circle play in scope selection, both he above have large imaging circles.

I observer under a Bortel 4 sky, how much more will get out of say a 100 mm over a 130 mm? The other option I was considering was get a 130 mm APM f 9.2 for visual and then getting a 100 mm quad APO I could use for NV and as a grab and go.

 

[PeterW]

Think focal length! You need to get things fast, so using the TV 67mm afocal giving nearly 2.5x faster than native. I don’t try ink you need excess infocus for this @GavStar can confirm. Fast gives a brighter view. What you them see is determined by the effective focal length you have. So fast and big gives the same image scale as small and slow. Massive scopes just gives smaller fields of view, better suited to smaller objects. So ideally you will have several scope options with different focal lengths that you move your “eyepiece” between. Get over the aperture fever..... my last NV optic has a 16mm focal length!

Peter

[GavStar]

1 hour ago, Deadlake said:

F 5.6 with a flat field corrector? I was thinking of a TOA-130 with a reducer+flatterner for NV work and then I could attach an extender-Q for visual/planetary. Or is this trying to get too much utility out of one scope and best to go with separate telescopes. Also how much does the imaging circle play in scope selection, both he above have large imaging circles.

I observer under a Bortel 4 sky, how much more will get out of say a 100 mm over a 130 mm? The other option I was considering was get a 130 mm APM f 9.2 for visual and then getting a 100 mm quad APO I could use for NV and as a grab and go.

 

I’m not completely certain since I don’t image, but reducers/flatterners generally have a very short (55mm?) distance from the reducer to the focal plane which means that 2inch diagonals and eyepieces have much too long light paths for these to work, hence I’ve gone for petzval refractors where this isn’t an issue as I’m guaranteed to be at the right distance as long as it’s in focus. 
The key eyepiece to use with nv is the 67mm Televue to keep the effective speed as fast as possible and therefore for wide 4 degree fov for California, Rosette, North America, heart and soul etc a 650mm focal length fast scope like the 130fsq works really work. I enjoy the 85mm as it’s so much more portable but then I’m getting to nearly 6 degrees fov which is maybe a little large for this big nebulae objects. For the smaller objects like the horsehead, flame, monkey head, Pac-Man, and also galaxies and globulars I think you really need an 10 inch plus scope (I use a c11 edge (flatfield again!) and 16 inch dob) to be able to use high eg 67mm eyepieces to get the bright views but also get higher mag with smaller fov for these smaller objects. So for one scope maybe 130mm only but for two a c11/dob and a 100mm or less portable easy to mount refractor would be my preference with nv.

re imaging circle, yes it’s nice to have a big one otherwise eyepieces like the 67mm May start to showing vignetting but it’s less obvious for visual only, more for imaging.

Happy to answer any specific nv questions you have by pm?

Edited November 3, 2020 by GavStar

[Highburymark]

14 hours ago, GavStar said:

I did have a Takahashi Epsilon 130d and it’s a nice scope for visual nv work but didn’t give the crispness of the fsqs. Once I got the fsq85, the epsilon’s days were numbered.

 

I’ve been surprised just how sharp the Epsilon is at F/3.3 - though Gavin is right that the edges are a bit ragged with TV Plossls - with Panoptics they are much neater. But as I’m not imaging, it doesn’t bother me that much. At such low powers I’m normally focusing on the central two-thirds of the fov.
Interesting, more affordable alternatives to the Tak fsqs posted above though. Hadn’t seen either of these scopes before. There’s also a Sharpstar superfast Newtonian, though reviews have been patchy to say the least

[PeterW]

Pretty good “stack” in the focusser Mark, good thing you’re using an alt-as or the eyepiece could end up anywhere ;-)!!

Peter

[Deadlake]

On 03/11/2020 at 09:24, GavStar said:

I’m not completely certain since I don’t image, but reducers/flatterners generally have a very short (55mm?) distance from the reducer to the focal plane which means that 2inch diagonals and eyepieces have much too long light paths for these to work, hence I’ve gone for petzval refractors where this isn’t an issue as I’m guaranteed to be at the right distance as long as it’s in focus. 
The key eyepiece to use with nv is the 67mm Televue to keep the effective speed as fast as possible and therefore for wide 4 degree fov for California, Rosette, North America, heart and soul etc a 650mm focal length fast scope like the 130fsq works really work. I enjoy the 85mm as it’s so much more portable but then I’m getting to nearly 6 degrees fov which is maybe a little large for this big nebulae objects. For the smaller objects like the horsehead, flame, monkey head, Pac-Man, and also galaxies and globulars I think you really need an 10 inch plus scope (I use a c11 edge (flatfield again!) and 16 inch dob) to be able to use high eg 67mm eyepieces to get the bright views but also get higher mag with smaller fov for these smaller objects. So for one scope maybe 130mm only but for two a c11/dob and a 100mm or less portable easy to mount refractor would be my preference with nv.

re imaging circle, yes it’s nice to have a big one otherwise eyepieces like the 67mm May start to showing vignetting but it’s less obvious for visual only, more for imaging.

Happy to answer any specific nv questions you have by pm?

Are they on tools for calculating the modification of a focal point for a refractor when adding a reducer? Edit: This link here has a brief guide:

I did see this as well,

https://www.365astronomy.com/ts-apo130q-imaging-star-130mm-f-5.0-sextuplet-6-element-flatfield-imaging-apo-refractor-telescope-42mm-field-diameter-for-full-frame-camera-sensors.html

As far as a 10" scope what about these:

https://www.firstlightoptics.com/stellalyra-telescopes/stellalyra-10-f8-m-lrc-ritchey-chrtien-carbon-truss-telescope-ota.html

in fact for the price of the FSQ-130 I could get the above two scopes and  a TOA-130 for the same price 😀
 

Edited November 5, 2020 by Deadlake

[PeterW]

Refractor questions go to Gav... but when you use the 55mm plossl for afocal it doesn’t shift the focal position much, whereas adding a focal reducer pulls the focal position inwards. My “imaging newtonian” needs an extension to use normal ep, but focuses nicely without when I use my “0.5x” reducer in prime focus mode. 

F8 is slow for a scope to do NV with, best start faster as the 67mm Televue will speed stuff up 2.5x and you want to get down to around f2... or faster.

The f4/f5 carbon fibre tubed newtonians would be better, start faster and can be sped up nicely, you can add a coma corrector if you feel it needs it (I don’t with mine, but with a normal wide eyepiece I do). 
again all we are doing is finding a way to get a certain field of view (focal length) as bright as we can (fastest focal ratio).

 

Peter

[GavStar]

24 minutes ago, Deadlake said:

Are they on tools for calculating the modification of a focal point for a refractor when adding a reducer?

I'm presuming that the FSQ-130 is your most used, however they are now out of production and cost as much as a small car fro some people 😀.

I did see this as well,

https://www.365astronomy.com/ts-apo130q-imaging-star-130mm-f-5.0-sextuplet-6-element-flatfield-imaging-apo-refractor-telescope-42mm-field-diameter-for-full-frame-camera-sensors.html

As far as a 10" scope what about these:

https://www.firstlightoptics.com/stellalyra-telescopes/stellalyra-10-f8-m-lrc-ritchey-chrtien-carbon-truss-telescope-ota.html

in fact for the price of the FSQ-130 I could get the above two scopes and  a TOA-130 for the same price 😀
 

On your first question, sorry I’m not sure, it seems to vary from reducer to reducer.

Actually my most used scope for NV is currently my 103mm William optics Pegasus Binoscope with two nv monoculars but that’s another story 😉

In respect of the two scopes you link to, the first one won’t work work for visual nv use I think - it states in the link that it won’t work with 2 inch diagonals for visual use. 
 

Re the second one it may work but again I think you need to do some investigation regarding distances from focal plane etc to see if a 2 inch diagonal would work for visual (looks like you need a diagonal for comfortable observing)

Edited November 3, 2020 by GavStar

[Deadlake]

42 minutes ago, GavStar said:

On your first question, sorry I’m not sure, it seems to vary from reducer to reducer.

Actually my most used scope for NV is currently my 103mm William optics Pegasus Binoscope with two nv monoculars but that’s another story 😉

In respect of the two scopes you link to, the first one won’t work work for visual nv use I think - it states in the link that it won’t work with 2 inch diagonals for visual use. 
 

Re the second one it may work but again I think you need to do some investigation regarding distances from focal plane etc to see if a 2 inch diagonal would work for visual (looks like you need a diagonal for comfortable observing)

By the way the 121mm sharpstar you linked to is also at 365:

https://www.365astronomy.com/sharpstar-121sdq-121mm-f-5.6-quintuplet-apochromatic-refractor-telescope.html

A lot better price...

[GavStar]

14 minutes ago, Deadlake said:

By the way the 121mm sharpstar you linked to is also at 365:

https://www.365astronomy.com/sharpstar-121sdq-121mm-f-5.6-quintuplet-apochromatic-refractor-telescope.html

A lot better price...

Great spot. Before I got the fsq130, I was very tempted by that 121sdq and with the 67mm plossl it would give a effective f2.2, very nice for afocal nv! With a 5 lens refractor there is a risk of miscollimation (fsqs have this issue sometimes as well) but it’s a lot lighter (and cheaper!!) than the fsq130 - I like it!

Edited November 3, 2020 by GavStar

[Deadlake]

20 hours ago, GavStar said:

Great spot. Before I got the fsq130, I was very tempted by that 121sdq and with the 67mm plossl it would give a effective f2.2, very nice for afocal nv! With a 5 lens refractor there is a risk of miscollimation (fsqs have this issue sometimes as well) but it’s a lot lighter (and cheaper!!) than the fsq130 - I like it!

Reading CN threads I can see following scope being used with NV and a focal reducer

Tak 100FC
Celestron 11 Edge
TEC 140 APO 
APM 130 APO LZOS F/6.7 to F/4.4

So possible, but the lack of flat field is the issue.

 

Edited November 4, 2020 by Deadlake

[GavStar]

51 minutes ago, Deadlake said:

Reading CN threads I can see following scope being used with NV and a focal reducer

Tak 100FC
Celestron 11 Edge
TEC 140 APO 
APM 130 APO LZOS F/6.7 to F/4.4

So possible, but the lack of flat field is the issue.

 

I use a 0.7x reducer with my c11 edge very successfully and with flat field.

I also use a 0.75x revelation rc reducer with my Ap stowaway, and a 0.75x ap photo visual telecompressor with my AP130gtx and tec 160fl, all with nice results. However the introduction of the 67mm Televue has meant less need for me to use reducers with my refractors since the 67mm produces enough reduction for nv. In addition, as you say, I do like the flatter fields and faster speeds of my fsqs which do seem to work better with nv than my other refractors (although they do work well).

Edited November 4, 2020 by GavStar

[Highburymark]

56 minutes ago, GavStar said:

I use a 0.7x reducer with my c11 edge very successfully and with flat field.

I also use a 0.75x revelation rc reducer with my Ap stowaway, and a 0.75x ap photo visual telecompressor with my AP130gtx and tec 160fl, all with nice results. However the introduction of the 67mm Televue has meant less need for me to use reducers with my refractors since the 67mm produces enough reduction for nv. In addition, as you say, I do like the flatter fields and faster speeds of my fsqs which do seem to work better with nv than my other refractors (although they do work well).

I’m the same Gavin - haven’t used a reducer since the 67mm adapter arrived. 

[Deadlake]

Can you calculate the apparent F number or is it just fast enough. For instance the Sharpstar is F/5.7 and then adding the 67 mm adapter and it become an effective F/2.2 from comment above?

[GavStar]

2 minutes ago, Deadlake said:

Can you calculate the apparent F number or is it just fast enough. For instance the Sharpstar is F/5.7 and then adding the 67 mm adapter and it become an effective F/2.2 from comment above?

In my experience below f2.5 is really where I aim for nv emission nebulae observation. Once it gets to this point, I become more concerned with aesthetics of view such as edge stars etc

[Highburymark]

At these superfast speeds, the biggest variable in a highly light polluted environment like mine is seeing/atmosphere. The difference from day to day can be dramatic, just like it can with conventional telescope astronomy. The other key variable of course is your tube specs. FoM, gain, EBI, SNR. Once you get down to really fast speeds, these other factors become much more important than trying to push the speed up further. It keeps things interesting though - never know quite what you’re going to get each evening. I guess things are more predictable if you have darker skies. Every time I’ve taken my gear outside London I’ve had more consistent performance.

[Space Hopper]

I'd love to have a go at NV someday, but know fairly little about the pros and cons.

Eddgie, On CN (NV & binoviewer guru)  uses a Boren Simon Astrograph to good effect, i believe.

Maybe worth a look and doing a bit of research on. A bit cheaper too !!

They are listed at the bottom of the linked page...

https://www.teleskop-express.de/shop/index.php/language/en/cat/c221_TS-Optics-ONTC---UNC-Newtonians.html