Louis D

On many refractors, they won't slide in from the front because the tube widens just ahead of the focuser where the finder shoe is mounted, so there isn't enough clearance.  Otherwise, I have no idea why they are designed that way.

Perhaps @jetstream could chime in here.  I believe he observes from Canada which gets quite cold in the winter as well.

You keep all of your aperture but experience vignetting in the outer field by shortening your truss poles.

You didn't say if you wear eyeglasses and if so how strong your astigmatism is and if you have presbyopia.  Do you need to refocus stars center to edge that you didn't use to have to?  If so, you may be getting presbyopia and can no longer accommodate near/far focusing.  If that is the case, you'll need to find flatter field scopes and eyepieces.

Astigmatism in you eye would be visible center to edge and would be stronger in lower power eyepieces.  This doesn't seem to be the case based on you description.

The scintillation is worrisome.  I recently had vitreous detachment diagnosed in my non-observing eye which causes random flashes in my vision.  It has to be watched to make sure it doesn't lead to retinal detachment.

Definitely get to an optometrist for a thorough eye exam.

2 hours ago, globular said:

Louis, your comment above prompted me to look closely at my Celestron #93519 diagonal and I discovered the barrel does indeed unscrew revealing a 2" SCT female thread on the eyepiece side of the diagonal.

I've ordered a baader 2" SCT male to 2" SCT male inverter ring that will then allow connection of a 2" baader clicklock SCT onto the eyepiece side of the diagonal - giving me the very nice clicklock mechanism I was after to hold my eyepieces in place.

Thank you so much for your help.

Sounds good.  Let us know how it works out.

The GSO/Revelation 2" diagonal also uses an SCT thread.  I screw an SCT threaded extension tube into it and then thread a TSFLAT2 field flattener onto the other end's M48 thread to flatten my refractors' fields.

Yes, you'll be moving your scope's mirror well away from its optimal design position to counteract the increased back focal distance.  There would be a touch more spherical aberration.

Alternatively, you can substitute nylon screws for the metal ones.  Probably M3 or M4 screws would work.

Note where the focal plane of the camera (sometimes marked with a line through a circle on the side of the camera body) is relative to the top of the focuser when it is in focus.  This is approximately the distance the shoulder of the eyepiece (where the insertion barrel meets the upper barrel) needs to be to reach focus.

If the diagonal uses a compression ring, it won't mark your eyepieces.

Baader is the only brand with interchangeable barrels on their diagonals to my knowledge.

Personally, I really like the GSO/Revelation dielectric diagonals.  They do have compression rings on both the 2" holder and the 1.25" low profile adapter.

I've never seen kidney beaning either with this line of eyepieces.  Since the blackout touches the edge in your image, it's not kidney beaning you're seeing.  Even in extreme kidney beaning, there will always be at least a thin line of visible image near the field stop as you can see in my composite image below:

There is a very slight hint of kidney beaning in the 12mm through 25mm versions as seen above, but it was undetectable visually.  As such, I would imagine the 8mm below would perform similarly.

What you're seeing is probably caused by being too close.  Back off from the eyepiece and approach it slowly until the field stop just pops into view.  That's the distance you should be observing from.  Twist up the eye guard to position your eye at that distance.

The original T1 11mm or the T6 11mm?  The former was very rare because it was quickly discontinued due to poor sales.

If your budget is tight, the BST Starguider 5mm is quite good for the money.  Here's a composite image of my ~5mm eyepieces I took through my field flattened 72ED refractor:

On 17/08/2020 at 06:26, Joe beaumont said:

Hi all, 

what is the best eyepiece brands and size for planetary viewing 

thanks 

Well, the Tak TOEs and Vixen HRs are both very good for highest power viewing, although the HRs are getting difficult to find.  The TeleVue DeLites are a small step down in ultimate contrast but have much better eye relief and a larger field of view.

11 hours ago, John said:

There are some ideas in this thread:

 

Just one or two or a few thousand. 😄

I would think you would only see the specs when lunar or solar viewing.

The wider field allowed by using 2" eyepieces more than makes up for the focal length extension to somewhere around 1700mm to 1800mm.  I also didn't notice any increased spherical aberration at higher powers.  People who mount a focuser on the rear threads have the same focal length extension issue, and I haven't heard them complaining about it on here.

If your 127mm scope didn't come with SCT threads already, you'll need this adapter and a 2" visual back.  There is vignetting in the outer field, but it isn't very noticeable visually.  What is noticeable is when bright objects pass the edge of the rear baffle, you get an oval shape that grows larger the farther off axis that bright objects gets.  Just recenter it and it goes away.

You can judge from these images I took through my 127 Mak demonstrating the additional field gained by using a 2" eyepiece versus a 1.25" eyepiece and the vignetting.  I realize now I didn't use a 1.25" visual back for the first image, so it might be about 12% to 15% wider with one.  At 85% center to edge, I sampled the luminosity of the lower image to be 65% of the center luminosity.

For visual, if you're mono-viewing (one eyepiece), and you don't have astigmatism, you can probably observe with your eyeglasses removed because you can focus out your distance correction.  As such, you can use eyepieces with limited eye relief.

If you have astigmatism, you'll probably need eyeglasses or possibly a TeleVue Dioptrx to correct out your astigmatism, depending on how strong your astigmatism is and what exit pupil your telescope/eyepiece combination is operating at.  As such, you'll need to use eyepieces with at least 15mm to 20mm of eye relief to accommodate either your eyeglasses or the Dioptrx.

In either case, since you're only using one eye to observe, the other one won't be looking at much.  If it still bothers you, you can cover the non-observing eye with an eye patch.

If you're binoviewing (two eyepieces), you'll need your eyeglasses since your eyes focus at different distances.

Low cost R&P focusers generally don't have any adjustment mechanism(s) to reduce the wobble you're experiencing.  Shimming the tube is generally the best workaround short of upgrading the focuser.

I also have grown trees in my backyard limiting my view nowadays.  As a result, I plan my observing around what is visible to the south in the clear patches.  As the night moves on, I observe new targets that come into view.  For instance, to observe Jupiter and Saturn recently, I had to observe between 11pm and 1am.  First was Jupiter until Saturn cleared the trees and then Jupiter went behind a house after a bit.  I really miss my northerly views the most.  I'm looking at getting a second home for getaways and retirement that will have darker skies and better sight lines.

3 hours ago, rwilkey said:

I have found this, in fact, I have just sold my only two 100° eyepieces (Omegons) in favour of my trusted 82° eyepieces.

Did you find that them to actually be 100° eyepieces?  I have the Meade MWA equivalent in a 26mm, and I measured it to be around 78° to 83°, depending on how much SAEP you can tolerate.  As such, it's basically in the same class as 82° eyepieces.

1 minute ago, Pryce said:

In theory, given perfect seeing and no atmospheric disturbances or light polluting, would the potential practical power be higher or is it based on limitations of the equipment, is kind of what I mean.

More specifically, it's based on the Rayleigh criterion.  Wikipedia has a good article on angular resolution.

Depends on the criteria used.  If you're splitting double stars and just looking for elongation rather than a clean split, then that allows for a claim of higher working power.  Realistically, most beginners need not concern themselves with such technical esoterica.  John has pretty much nailed what is typically the maximum working power for your scope and observing conditions.  If on the other hand you were observing from certain coastlines, deserts, or coastal mountain tops with excellent seeing conditions and are using a 16" to 30" Dob, it's quite possible to successfully use powers in the 400x to 1000x range.

I would stick with the GSO/Revelation diagonals because the WO (Synta?) and its variants have a field stop of sorts at the bottom of the insertion barrel that vignettes widest field 1.25" eyepieces.  Since I use mine for binoviewing with 22mm clear aperture binoviewers, this doesn't matter to me, but it might to you.

2 hours ago, vlaiv said:

So I've heard:

6 hours ago, vlaiv said:

This really gives you idea of what barlow you want - one that is x2.5 (but in reality is closer to x2.2)

Totally missed that. 🤣  It's just one of those days.

3 hours ago, Kirby301 said:

@Louis D

I've read the bst eyepieces have removable eye cups and 16mm eye relief, im not sure how much of that eye relief would be usable?

With the eyecup removed, close to 15mm.

Don't most people report the GSO 2.5x to be closer to 2.2x?