Louis D

9 minutes ago, Don Pensack said:

But, a 10.5mm tall adapter allowed all the TeleVue 1.25" eyepieces to focus in the range of the Paracorr's travel, and no other height would have.

Couldn't they have simply designed the tunable top to have more travel range upward by 16.5mm and gone with a flush 1.25" adapter?  That would also negate the need for the High Hat adapter.  It might require a more clever extension design, but I have 1970s/1980s manual camera lenses and macro lenses that can extend 6 inches on internal helicals and maintain optical alignment, so I know it can be done.  Some even do it via nesting tubes to maintain compactness. 

The only issue would be getting it low enough to not need the In Travel adapter for any eyepieces.  Again, a more clever barrel extension design might have been workable here as well.

The Paracorr 2 costs over $500, so it's not like it's a budget device that couldn't afford to have better mechanicals.  All these adapters seem to scream that this was not a well thought out extension device.

1 hour ago, Mr Spock said:

I have an old Meade 4000 series 32mm Plössl. It is amazingly sharp. 

Is it one of the old Kowa made 5 element ones?  Those are exceptional if you can find them.

1 hour ago, vlaiv said:

That is quite odd.

32mm Plossl has very generous eye relief - around 22mm. I never had problems with eye relief in such way.

Perhaps the TV eye lens is recessed a bit much?

My Orion Sirius Plossl 32mm has the eye lens recessed so much that I can only just use it with eyeglasses.  The 26mm version is recessed a similar amount, making it impossible to use with eyeglasses due to Plossl eye relief scaling with focal length.

I agree that the GSO 32mm Plossl is quite good.  Some folks rave about the Vixen NPL 30mm, but at the end of the day, it's still a Plossl at twice the price, and that will show as astigmatism at f/5 at the edge of the field.

I would get the Nirvana-ES UWA-82º 7mm and 10mm instead of the Luminos 7mm and 10mm.  Performance-wise, they're very similar, but the Nirvana eyepieces are much less expensive.

I keep mine in a large, vintage Tamrac camcorder case I had lying around underutilized.  It was intended to hold 1980s sized camcorders, so it swallows up the 127 Mak with ease. 😆

My daughter keeps hers in a gym duffle bag with the OTA wrapped in bubble wrap for protection.  The pockets are handy for storing accessories like spare batteries.

Did you flock the interior of each baffle tube as well?  That's where I'm getting most of my internal reflections in my 127 Mak.

I found this In-Travel adapter diagram showing the adapter differences graphically:

So, if like me, you are already using a low profile 1.25" to 2" adapter like the one that comes with GSO diagonals, the In-Travel adapter won't buy you anything outside of a Paracorr.  If there was a notch in the Paracorr tunable top for the 1.25" locking thumbscrew, you could probably use the GSO adapter in it.

My Dob's focuser also has this 2" insertion barrel notch to allow 1.25" and 2" eyepieces to be parfocal if both focus at the shoulder, which most of mine do.  I wonder why the Paracorr tunable top does not?

I can understand why folks would despise switching between 2" and 1.25" eyepieces if they are forced to be non-parfocal due to the construction of the 2" insertion barrel and 1.25" adapter combination as in the Paracorr.  It's already bad enough that my 10mm Delos focuses 0.25" below the shoulder forcing me to rack my focuser outward 0.25" relative to most of my other eyepieces.  I suppose I should just invest in 0.25"-worth of 1.25" inner diameter O-rings for it to parfocalize it.  I'm guessing TV thinks all 1.25" eyepieces should focus 0.25" below their shoulder, thus the 10.5mm height of their adapter.  Even that doesn't quite compute because 0.25" equals ~6mm.  What's with the extra ~4mm?

Reflectors did have a lot of problems back then.  Long focal ratio mirrors led to long, unwieldy OTAs and massive EQ mounts.  The ideas for Dobsonian mounts and EQ platforms hadn't yet dawned on anyone.  I'm not sure why short f-ratio mirrors took so long to be adopted even after the Dob mount and EQ platforms became popular.  Perhaps the eyepieces of the day looked terrible in them?  I don't think any new mirror grinding or testing methodologies have been invented for a long time.

You'll need about 75mm of space between the back of the CC optics section and the DSLR's imaging plane.  If you're using a T-ring, that alone gets you to 55mm spacing.  Thus, you'll need approximately 20mm of additional spacing.  I would think an M42 to M48 adapter would also be necessary plus some spacer ring(s) to get your to that 20mm.  I would invest in a spacer ring kit to fine tune the separation.  These kits say M42, but mine came as an M48 kit.

On 31/01/2023 at 05:43, Franklin said:

Have you tried the Wratten #11 yellow/green?

I recently picked up a used Hirsch Light Green #11 which is more teal and less yellow than the Wratten standard.  I ran it through my spectrograph and found it passes a lot of violet and red.  I confirmed this on Venus, Jupiter, and Sirius tonight in my f/5 ST80 while imparting very little green color cast.  It helped a bit, but it was not a complete solution.

I then paired it with Hirsch Yellow #12A which lies midway between Yellow #8 and Yellow #12, and is very similar to a cheap yellow filter from China, just with a sharper cutoff and less attenuation as I showed in an earlier spectrogram post.  This cut out the majority of the residual violet as my spectrograph tests predicted while imparting a noticeable yellow cast.  However, spurious red remained.

I next tried my Meade Green interference filter and my cheap green filter from China.  Both snuffed out all the spurious violet and red, but with a strong green cast.  According to the spectrograph testing, much or all blue and yellow/orange/orange-red also gets cut.

Finally, I ran all the Roscolux green, yellow-green, and blue-green filters through the spectrograph and chose the ones with the best cutoffs at each end to test tonight.  Those three were R86 Pea Green, R89 Moss Green, and R389 Chroma Green.  Of the three, the R89 Moss Green had the highest transmission and passed the most spectrum.  All three cutoff all visible spurious violet and red, so I declared R89 Most Green the winner based on providing the lightest touch.

I won't lie, the R89 Moss Green image is green to yellow-green, but it is much less intensely green than either the cheap green or Meade green filters while still cutting out all spurious violet and red.

I feel vindicated that it would be possible to create a yellow-green interference filter passing all the light from about 470nm (dark teal blue) to about 610nm (orange-red) to cut out all visible spurious violet and red in fast achromats.  For now, the R89 Moss Green filter works well enough because having about a 50% transmission in the central passband is not an issue on these super bright objects that show loads of spurious violet and red in fast achromats.  With all three super bright objects, clarity was greatly improved by cutting out unfocused light at both ends of the spectrum.  An interference filter with ~95% transmission in this central passband would open up the list of viewable objects to dimmer ones.  Splitting tight doubles would become easier as well.

I composited the spectrograph results for the various filters and filter combinations described earlier:

A filter with this passband would agree well with the spectral frequencies that are well focused by achromats (the dotted green line) below.  From just below 500nm to just above 600nm is about ideal.

23 hours ago, paulastro said:

In my post,  the gist was nothing to do with  'Fracts v Newts', only that a 4inch ED/Apo is not the best telescope scope for all objects on all occassions.

As an example, globular clusters in particular simply will not resolve at all in my 90mm APO FPL-53 triplet but resolve nicely in my 8" Dob.

2 hours ago, PeterC65 said:

My existing ES 68° 24mm gives me a 2.1° TFoV with the Explorer 150PDS. Unfortunately the 30mm UFF only increases that to 2.3°.

2 hours ago, Don Pensack said:

30mm --36.3  That is 33.5% wider than the 24mm ES 24x68 (2.1° becomes 2.8°)

I composited together the 24mm APM UFF (which has about the same TFOV and correction level as the 24mm ES-68) with the 30mm APM UFF to show the difference in TFOV, AFOV, and magnification:

You get a nice 33.3% increase in linear field of view with the 30mm over the 24mm APM UFF with much better edge correction and a wider AFOV.

On 11/02/2023 at 06:43, stormioV said:

I do like the idea of  StellaLyra 80 20mm . As my FL gap seems to be in 20-25mm for wider views, would Antares x1.6 Barlow be a worthwhile route? This would alter my 34mm to 21.25. This 34mm is my only 2inch ep. 

Long focal length eyepieces, especially 2" ones, don't do well in traditional Barlows.  The outer field will have a hard cutoff rather than soft vignetting due to the diverging outers rays caused by the Barlow not being captured at all by the eyepiece field lens.  This is why Tele Vue introduced the Panoptic Barlow Interface (PBI) for its 2" Big Barlow years ago.  It reconverges the light rays as in a telecentric magnifier like a TV Powermate.  As such, there is no vignetting or hard cutoff around the edges.

I use a PBI in a GSO ED 2x 2" Barlow as a poor man's 2" 2x Powermate because the GSO has nearly the same focal length as the TV Big Barlow.  However, you're getting a mighty long stack sticking out of your focuser.  This isn't much of a problem in a Dob with a sturdy focuser, but it would be a nightmare in an alt-az mounted small refractor to keep balanced.

56 minutes ago, PeterC65 said:

I've seen several positive reviews of the Aero ED 35mm which is what brought it to my attention, but your guess is that it may only be a bit better than the BHA 36mm. Given that you don't rate the BHA 36mm this is not a great endorsement of the Aero ED 35mm either! Yet you do have the Aero ED 35mm.

I'm trying to decide whether the TS-Optics Paracor UFL 35mm is worth a punt (about £130, which is above my usual punt territory).

The ED 35mm is going to be slightly better than the BHA 36mm, but not head and shoulders better.

Here are Ernests tests of the BHA 36mm, ED 35mm, and Panoptic 35mm for comparison.

Here are the entries from his index of tests below:

As you can see, the ED is slightly better than the BHA at the edge, but not hugely better and certainly not at Panoptic level correction.

4 hours ago, Franklin said:

I sold mine about 6 months ago, it was too long for my scopes and light pollution conditions here. Big chunky eyepiece!

 

I was thinking for use in my Mak to get to a 50mm/12 ~= 4mm exit pupil.

I wonder why the 45° AFOV?  55/56mm Plossls have 50° AFOVs.  Perhaps it's design was some sort of Abbe orthoscopic variant?

4 hours ago, Froeng said:

This is a very interesting discussion. It highlights the subjectivity of each observer’s personal impression.

I did a direct comparison of the old LV30 and the new NLVW30 in a friend’s C11. The only significant difference to my eye was the slightly wider field of view.

Thinking further about this - it may have to do with my eyesight, as I have astigmatism. I am wearing glasses that correct for this while observing. Maybe the glasses level out the optical differences? Or maybe the view could be sharper in either of the eyepieces…?

Thank you for all input.

Frank

Or maybe it was the use of an f/10 system to make the comparison that leveled out the differences?  Had you made the comparison in f/6 or faster scopes, your impressions might have been different.

I have both the 35mm Aero ED and the 40mm Lacerta ED.  The 40mm is noticeably better corrected than the 35mm.  However, the 35mm has a noticeably wider AFOV and nearly the same TFOV thanks to its 44.4mm field stop diameter.  If I had to guess, the 35 ED is probably a bit better than the 36mm BHA, but not substantially better.  It will probably have a significantly wider TFOV.

The old, massive 35mm Baader Scopos Extreme that was replaced by the 36mm BHA is sharp edge to edge at f/6 and probably close to that at f/5 being a massive negative/positive design not much affected by fast f-ratios.

Take a look at my Lacerta ED 40mm write-up.  I think I have an image showing all three FOVs for comparison somewhere in it.

I've never been even remotely interested in the 36mm BHA due to poor correction reports and high price, so I cannot directly comment on how it compares.

The one low powered LV/NLVW that I'd like acquire someday would be the 50mm LV.  By all accounts I've read, it was an excellent ultralow power eyepiece with no modern peer.  The problem is, unless you come across one as new old stock in some small, old, out of the way astro/photo shop, you'll never be able to purchase one new or used.  I can't recall the last time I saw one up for sale on CN or anywhere else used.

FPL-51 in my 72ED pretty obviously shows violet fringing at higher powers.  It's only going to be worse at 102mm even at the same f-ratio.  My 90mm FPL-53 triplet doesn't show violet fringing at pretty much any power, but it has red-green out of focus images on either side of best focus that merge to white in focus.  It's definitely not reflector-like.  I don't know if FPL-53 doublets behave this way as well.  Overall, I much prefer the 90mm to the 72mm scope.

Avoid the illuminators that have the fat back end.  I've had nothing but problems with the switch desoldering from the wiring.

I've had much better luck with the slim, straight style illuminators found on Celestron eyepieces.

3 hours ago, Peter Drew said:

I'm not disagreeing but you could probably get a used 80mm f5 telescope for around the price of a focal reducer.  I wouldn't be too optimistic about the field characteristics of a telescope at the severe reduction of a 0.5x FR.    🙂

How hard would it be to find a matching doublet and the correct distance to place it in the tube to make a poor man's Petzval or Aplanat design?

3 hours ago, Highburymark said:

Would be interested to see any pics you have of the Scopos Louis

The BSE 35mm is fifth from the left below and the fifth ruler image down from the top in the FOV images.

Notice the fairly low radial edge distortion in the BSE 35mm.  It's 17% versus 47% for the Meade 5000 SWA 40mm.  This makes viewing objects like the moon more enjoyable because they are distorted less as they drift across the FOV in an undriven mount.

The BSE 35mm is in the back row, second from the right, to the immediate right of the ES-92 17mm.  Weight and size wise, it's a good observing companion to the two ES-92s as I said above.

I don't have an image of the eye lens, but it is the largest of all my commercially made eyepieces at 47mm.  Even with 17mm of eye lens recession, it still has 17mm of usable eye relief.  I once unscrewed the top to see what 34mm of usable eye relief would feel like.  It felt like way too much eye relief even while wearing eyeglasses. 😅

Here's a CN user's image with the top removed from the Orion Stratus 35mm version in a CN thread about it:

You don't dare turn the eyepiece in that state.  That eye lens will drop right out without the top screwed on.  I created a low profile top from a large pill bottle cut to size and with the threaded neck cut off.  I rubber band it on top against the rubber grip to hold the eye lens in place when I remove the top.

That's a great deal, but they don't ship to the US.  Explore Scientific (the US Vixen distributor) still has it at $249 before tax.

2 hours ago, Zermelo said:

The one point I might disagree with you is where you say "as its price decreases from its initial offering"  ... I suspect the price may go up, as more reviews get written 😃

Interestingly enough, the price before Christmas went as low as just under $100 before taxes on ebay-US for a day before bouncing back up again.  I'm guessing someone was testing the waters to see if the demand would noticeably go up if the price went significantly down.  Hopefully they don't try price testing in the opposite direction to see what the market will bear.  Explore Scientific certainly has done this in recent years with most of their offerings.