Louis D

Given the super short focal length of your scope, you're probably going to have to either use a Barlow or tele-extender to get the power up to a reasonable level for planetary observations.  Alternatively, if you are opposed to adding additional glass to the optical path, you could look for used Vixen HRs which were available in 3.4mm, 2.4mm, 2.0mm, and 1.6mm focal lengths.  Tak TOE eyepieces are still available new in 4mm, 3.3mm, and 2.5mm focal lengths.

Why stop there?  Start with this nice 20" APO lens from Russia and build your own scope around it.  It's a bit of a bummer it's gone up 100,000 Euros in the last couple of years, but you could probably talk them down a bit since it's been sitting on the shelf for a while now.

2 minutes ago, Mr Spock said:

Same here. My 80mm doesn't even have a finder though  The 42mm LVW gives 5°, so, no need.

Although I find it nice to not have to swap out a high power eyepiece for my ~40mm SWA if I step away from the scope to relocate an object that has drifted out of the FOV in the interim.  The RACI can get me back on track again pretty quickly.  Lately, I've been using my GLP more than either my Rigel QF or my Telrad, though, to get in the general vicinity.  It's much less of a struggle to use for someone with a bad neck and back.

1 hour ago, Alan White said:

I am sure that all Don says is correct,
but If I do these things, then I could only observe about 1 night per year!
 

Unless you move to a more optimal place to observe to increase your chances.

11 minutes ago, M40 said:

I would be interested to know, has anybody used zoom eyepieces with binoviewers? 

Absolutely, lots of folks including me.  It's probably one of the best uses for them because swapping two eyepieces and making sure they're not tipped is a royal pain.  Matching magnification is relative simple.  I just rotate the zoom collar on both until my dominant eye sees the best image, and then I fine tune the other zoom's magnification to match.  Your brain instinctively knows when they match and you stop zooming then.  At that point, you have clear binovision again.

They give you the ability to quickly find the optimal magnification for the current seeing conditions relative to the object being viewed.

Keep the finder scope closer to the focuser than the Telrad since you probably ping-pong back and forth between the two as you zero in on an object.  I generally only use the Telrad to get me in the vicinity of an object and don't generally look back unless I need to reset my bearings if my fine grained search goes way off the rails.  As such, the Telrad can be placed on the other side of the finder scope away from the focuser.  However, if there is enough separation between the focuser and the finder scope, you may be able to position the Telrad between the two, but further down the tube away from the end.  Just make sure you can bend yourself around to see up through it.

1 hour ago, MalcolmM said:

Is the star transit timing experiment (which I will attempt when the rain and clouds disappear!) saying that the magnification is proportional to the field of view? This will be a little tricky for me as without the 1.6x in front of the diagonal I cannot achieve focus. But hopefully I'll get a close enough result. I can then compare that with globular's formula.

Yes, magnification is proportional to the true field of view.  If you halve the TFOV, you must have doubled your magnification if all else is constant.

That's the beauty of the ruler method.  All that extra optical path length through the BV allows you to reach close focus easier.  It's the same as adding an extension tube of equivalent optical length.  Give it a try and see if you can reach close focus with the GV without the 1.6x.  By close, I mean somewhere between 10 and 50 meters.  You're never going to reach focus on something a foot away without an insane amount of extension. 😁

In my experience, the Morpheus line is much better corrected at f/6 than cheaper 70 degree eyepieces like the Omegon Redline and similar.  I lump the Hyperions in with the Redline type eyepieces.  They're much better than a bare 70 degree Erfle or Konig, but they're not quite there as far as edge correction when compared to the Morpheus, Pentax XW, and Delos lines.  It's a matter of how picky you are about edge astigmatism and how far your budget will stretch as to which line to buy.

34 minutes ago, Andrew_B said:

Newtonians have their advantages but there's a reason that two, and increasingly three-mirror designs are the standard at the high end. More mirrors allow you to have greater correction across the entire field but they obviously cost more to make and collimation is more of an issue.

That's certainly true of observatory class telescopes, but a large Newtonian with a hand figured mirror and Paracorr II is hard to beat dollar for dollar on aperture at the high end of the amateur market.  Most folks dropping $20,000+ on catadioptric designs are purely imagers, not visual observers.  On the other hand, folks dropping $20,000+ on giant custom Dobs with Zambuto or similar mirrors tend to be visual only observers.  It really depends on what you're going to use the telescope for when it comes to deciding on a particular design at a particular price point.

My 20+ year old Dob is made from 3/4" oak plywood and sonotube.  Heavy for its size, but both have stood up to being banged into doorways and accidentally kicked without visible injury.

Luckily for you, the Powermate doesn't grow significantly in power with increasing separation.  As such, you should just be able to multiply the various magnification values together.  As a double-check, setup a ruler or similar and make some field of view measurements without the BV, with the BV and OCA, and with the BV, OCA, and PM.  Eyepiece choice shouldn't matter since all you're looking to calculate is the differential magnification between each step.  These values will remain more or less constant regardless of eyepiece magnification.  This is how I determined that my Meade 140 2x Barlow nosepiece yields exactly 3x in my BV.

16 hours ago, Highburymark said:

Lots of atmospheric colour on Jupiter this evening. 
Is anyone using an ADC successfully? They look like another great lump of metal to add to the eyepiece stack, but are they effective for the planets?

I've not used one myself since I'm about 22 degrees latitude south of you, so planets generally get high enough for AD to be a non-issue if I wait for them to be due south.  However, I've read many reports that they work really well.  Keep in mind that they require a fair amount of in-focus, so check how much you have left with your favorite eyepieces at best focus before buying an ADC.

6 hours ago, wookie1965 said:

I have a Meade 127mm on a EQ5 mount with a EQ6 tripod adapter plate and pier extension works very well for visual only as it is at the top end on the mounts load capacity.

All I can say is, it's a good thing the Dobsonian mount was invented if that frac is at the top end of an EQ5's capacity.  Can you imagine how big of a GEM it would take to mount a 24" Newtonian?  It's no wonder all modern giant observatory telescopes have gone to alt-az mounts.

21 hours ago, Beulah said:

if I need to get away from the second moon that is my neighbour's light

Sounds like you either need to have a serious conversation with your neighbor, or setup a spotlight shining in their bedroom window if they're recalcitrant.

12 minutes ago, Ian McCallum said:

Some of those StellaLyra ones look tempting...🤔

https://www.firstlightoptics.com/stellalyra-telescopes/stellalyra-12-f5-dobsonian.html

Above 10", I would seriously consider going with truss Dob.  Weight and tube size take a serious jump at 12"

1 hour ago, Ian McCallum said:

Are any of the SW ST series of refractors suitable for visual observing?

For low power views they would probably be fine.  You could always add a Baader Contrast Booster to suppress all purple and deep blue light if the color fringing bothers you.

At high powers, their chromatic and spherical aberrations would detract from the view.  It really depends on what you want out of a refractor.

2 hours ago, Space Hopper said:

Also the 35Pan i have won't work with my Newtonian.

What's the issue?  Since it focuses below the reference plane (eyepiece shoulder), in-focus shouldn't be an issue.  It's also well corrected to at least f/4.  Is it just the large exit pupil bothering you?  It should still work well as a finder eyepiece, just with a washed out background sky.

A big ole Howdy Pardner from Texas!

Agreed @JTEC.  I couldn't get my 19mm Russell Konig pair to merge at all last Friday despite my best debugging attempts, so the new SVBONY 20mm UWA eyepieces replaced them in the BV case.

1 hour ago, JTEC said:

There’s probably a little bit of a knack about using binos but in terms of viewing technique I honestly don’t feel it’s much different from using ‘ordinary’ binoculars.

Well, except for the fact that BVs are firmly attached to a large object making eye/BV alignment a much bigger challenge than with handheld binoculars.  With cyclops viewing, it doesn't matter at what angle you come in at the eyepiece or even if your face is square on with it.  All this matters immensely with BVs.  As such, I have to get my observing chair "just so" in front of the BV so I can comfortably align my head and eyes to the BV.  I can rotate the BV in the focuser, but I can't tip them up/down or swing them left/right because, again, they're attached to a large object, the OTA.  As such, I have to be really motivated to get them out.  Things like planetary oppositions and such motivate me.  For casual panning about the skies, I prefer monovision.

Make sure to give that triplet plenty of time to acclimate.  I have to allow 30+ minutes for my 90mm triplet to equilibrate before the spikes around stars settle down.  The first time I looked through it, I freaked out thinking it had pinched optics.  It just needed time outside to settle down.

Agreed on GCs and BVs.  I had very relaxing views of M22 last Friday night.  I don't know that I could make out any more stars across the core in bino vs mono mode, but the steadiness of the view improved with two eyes such that I could study it more easily.

3 hours ago, Rainmaker said:

I owned both the E21 and N22, I now own only the N22 as I didn’t really find the 100 degree field easy to view…

The N22 is just so easy to use….

You might like the 17mm ES-92.  It gives up very little in TFOV to the 22mm NT4 while still being easy to use with eyeglasses.  The whole AFOV is easy to take in.  It's just there in front of your eye like a big picture window.

IIRC, I bought my 22mm NT4 from a seller who replaced his with a 17mm ES-92.  I like them both, so I've kept both.

Do you have astigmatism in your observing eye?  If it is greater than 0.5 diopters (check CYL section of your eyeglass prescription), you'll want to either wear eyeglasses or use a Dioptrx.  If this is the case, the 22mm NT4 comes highly recommended.  If not, you could go with the 21mm Ethos or a 20mm APM XWA HDC (or other brandings) if cost is an issue.

Well, I'm guessing from your avatar that you already have an 8" Dob.  A 3" to 4" ED or APO refractor can nicely complement such an instrument for wide star field views, splitting tight, uneven double stars, etc. thanks to their tight star images.

I would suggest starting with an ED doublet because triplets are very slow to acclimate.  Cheap, short tube achromats often have loads of spherical aberration and purple fringing.  I was put off by my ST80 because of both.  My 72ED changed all that.  I then moved up to a 90mm FPL-53 triplet for more general use.  However, I have to think ahead and set it out the equilibrate, or I'll have spiky stars for 30 minutes or more.  The 72ED does not have this issue being a smaller doublet.