Louis D

I had a spare moment today, so I setup my 90mm APO with the triple finder mount with a couple of combinations of nighttime and solar finders from different angles.

I had it backward in the above post about where I put the GLP and QuikFinder.  The GLP protrudes too far back to be in the top position and the QF sits up high enough to not have eyepiece interference.

The phone is for when I use SkEye to locate difficult objects.  I forgot to take a picture from underneath, so I'm including an earlier image of the bracket I made for it.

Notice how the 9x50mm RACI sits perfectly in line with the plane of the altitude axis for best balance.

I couldn't think of a useful third solar finder, so I left a finder shoe empty.

1 hour ago, Alien 13 said:

I have one of these...

 

Nice microscope too 😀

Alan

I had one of those from the 70s as a kid.  I wonder what ever happened to it?  Plastic singlet lenses made for some very distorted/chromatically smeared views as I recall.

You want the the CG (center of gravity) of your setup to pass directly through each rotational axis.  I'm guessing your DEC axis has bits and bobs hanging asymmetrically off of your OTA forcing the CG in that axis of rotation above or below the actual rotational axis.  It's probably directly above or below it with the OTA horizontal, so it balances nicely in that orientation.

I have a similar issue visually with my alt-az mount at high altitudes when using heavy eyepieces.  The weight protruding up and away from the diagonal has to be counterbalanced by a similar amount of weight protruding down and away from the OTA on the other side of the altitude axis to prevent my rig from turning turtle.

I'd say everyone needs a quality 32mm Plossl as a frame of reference when building out an eyepiece collection.  They're not that expensive and punch well above their cost.

I haven't tried a 32mm GSO Plossl in an f/5 scope in recent memory, but it will perform quite decently as compared to the cheaper, moderate wide field eyepieces like the Starguiders.  It's also sold under the Revelation brand in the UK.  Look for Taiwan instead of China for country of origin.

I don't know how well the 32mm Celestron Omni, Skywatcher SP and other Chinese sourced Plossls (Synta possibly?) stack up against it having never used them.  All are 4 element symmetric designs in actuality.  Differences come down to attention to details such as quality of lens polish and figure, quality of multi-coatings, and stray light control.

Tele Vue Plossls will have better edge sharpness in fast scopes thanks to their convex instead of planar outward facing surfaces, but not enough to justify their pricing.

Here are comparison images through some of my eyepieces using a phone's camera in those focal length ranges to give you some idea of what the resultant image looks like.  The telescope used was a 72ED f/6 refractor.

The 25mm Paradigm is the same as the BST Starguider and the 32m Plossls will look very similar to the 30mm NPL.  Open them at full image scale to get a better idea of the differences since the pixel scale is the same at that point.  Notice how much sharper the Plossls are at the edge compared with the 25mm Paradigm/Starguider.  Also notice that the former are showing slightly more true field of view than the latter.  You would need to move up to a 24mm APM UFF to get similar true field and edge sharpness as the 32mm Plossls.

The higher power, wider field eyepiece will show objects at a larger image scale with a darker background leading to better contast.

On the other hand, at a given price point, the higher power, wider field eyepiece will generally be less well corrected edge to edge.

The 25mm BST Starguider is not sharp to the edge at f/6, let alone f/5, in my experience.

If your budget were a bit higher, I'd say the Sky-Watcher SkyMax-127 AZ5 Deluxe for £495.  Fairly compact except for the tripod legs.  I put together a similar setup for my daughter's camping trips.

Next, I would got with a Sky-Watcher Heritage-150P Flextube Dobsonian Telescope for £238 on a photo tripod with a ball head of unknown cost along with a dovetail clamp as pictured below:

Either one would be fairly compact and transportable and yet would show you solar system objects with ease.

Budget, transportation, weight limits, setup time, etc. limits please.

14 hours ago, Highburymark said:

Looks even smaller in use with my 6ft 5ins frame draped over the eyepiece.

Wait, don't you mean 196cm or 1.96m frame?  I've been led to believe by folks on SGL in other threads that only Americans are foolish enough to carry on using non-metric units in any capacity.  That's my two penn'orth (or is it two pennies worth or two cents worth?).

As far as small telescopes, I've got a 60mm Russell Optics OTA adapted from a binocular tube that works well as a RACI scope with a 90 degree correct image prism.  I've also got a 60mm Kasai PIco-6 Mak with loads of spherical aberrations.  I've got a home built PVC and gaffers tape finder scope using a military surplus 63mm achromat of about f/4 and two 2" right angle surplus prisms mounted 90 degrees to each other.  It will accept any 2" eyepiece for insanely low power views.

9 hours ago, Mr Spock said:

I have the 12" Dob, and to me the included 30mm is absolute pants.

Could you elaborate?  Is it blurry across the entire field, only at the edges, suffers from massive field curvature and/or kidney beaning galore, etc.????

Is it the same as the 30mm GSO SuperView 2" eyepiece?

Is it less sharp in the inner 50 degrees than a typical 32mm Plossl?

Pinholes can be safely covered with dots of opaque fingernail polish without significantly affecting optical performance.

Found a US Amazon seller and sent the link to the wife (who has Amazon Prime) as a "gift suggestion".  She kind of owes me a Valentine's Day gift I actually want.  We'll see if I get it.

Yep, appears to be the same part.

Okay, how about this one?

5 hours ago, wookie1965 said:

15mm is the best of the bunch.

I found the 12mm to be the best of the Starguider BSTs.  The 15mm was only marginally better than the 18mm.  Read my critic of each eyepiece in a comparative shootout:

Is this what you're looking for?

1 hour ago, spacegalaxy said:

Yeah, I was looking at the zooms because of that, they are lightweight and no need to take three eyepieces and a Barlow for a observing session

I would take a 24mm to 32mm widest field eyepiece along to supplement the zoom.  If your scope can handle the power, a shorty Barlow might pair nicely with the zoom to get to higher powers.

3 hours ago, mikeDnight said:

This morning I received from Starman53 a 32mm Celestron Erfle, which is an identical match to the one I already have. These are really little jewels, and can run rings around more pricey name brands from high end suppliers.  Obviously these two will now be used as a binoviewer pair, and should be sweet in my 6" F10. 

Is that a circle-V maker mark for Vixen I spy on the Celestron?  Vixen sure did make a lot of really good eyepieces back in the day.

On 30/01/2022 at 08:34, John said:

The last thing that APM will want to do is to put out something with less than impressive performance. Forums such as SGL and CN mean that word gets around really quickly and once something gets a few wavering reports, it is very hard to pull it back from that setback I think.

The damage from a delay, even a long one, can be overcome if the product turns out to be a good one in the end.

So true.  The Celestron Luminos and Meade MWA lines never really recovered from poor reports by early adopters.  MWAs were discontinued after just a few years.

On the other hand, everyone praises the 17.5mm Morpheus even after a 3 year wait for it.

If early adopters report that eye relief works for eyeglass wearers and the quality of the image is a good step up from the BHZ, I'll probably get one of these new zooms.

I really like the 20mm version in my Barlowed binoviewer, but it isn't very good at f/6.

How is the exit pupil behavior of the 6mm?  I've read that the 6mm and 9mm versions suffer from kidney beaning (SAEP) which requires careful eye placement.

So, the 22mm LVW could conceivably be similar to a Panoptic design (4 groups, 6 elements):

I wonder if anyone ever did a shootout between it and the 22mm Panoptic. 🤔

1 hour ago, iapa said:

My tu’pence worth

Most telescopes are designed to focus light on a curved surface - the back of MK1 eyeball.

Most folks use an eyepiece to view the image from the telescope rather than view the aerial image directly.  Eyepieces themselves may have curved or flat focal planes that may or may not match the curvature of the telescope's focal plane.

Coma is generally caused by projecting light on to a flat surface, camera sensor.

Coma is inherent with a Newtonian's paraboloidal figure.  It has nothing to due with the curvature of its focal plane.

I suspect that unless you have have a particularly bad optical path, you wouldn’t experience a bread deal of difference at the edges of the image.

Have you ever looked through an f/4 Newtonian using an ultrawide eyepiece?  Coma is blatantly obvious in them if you're used to a coma-free field.

you could see an increase in apparent light levels 9brighter images) as most correctors are focal reducers, for example the corrector I have on 8" SCT reduces focal length from c2000mm to 1280mm, and focal ration from f10 to f6.3

Perhaps in an SCT, but the OP specifically asked about Newtonian coma correctors.  Visual Newtonian coma correctors usually are mild focal extenders.

See inline comments above.

32 minutes ago, jetstream said:

Kinda makes me wonder why others (than China) use Ohara and Schott but charge so much more...

Labor and overhead costs are very low in China compared to the US and Europe.

6 hours ago, Mr Spock said:

The Vixen LVW is a similar 6 element design.

Which, the 42mm?  The rest are 7 or 8 element negative/positive designs as far as I can recollect.

6 hours ago, Mr Spock said:

As the Wild design preceded the Panoptic by 30 years I think you meant the Panoptic is reminiscent of the Wild design

The only non-Nagler patent cited by Al in that patent application was for the Scidmore.  I thought he might have cited the Wild design, but he didn't.