Louis D

3 hours ago, apaulo said:

i too would agree about the baader morphs for life long  use.  id say money well spent but shop around for prices.

I'd also recommend the Pentax XWs.  The 1.25" ones are $30 cheaper than the Morpheus right now in the US.

4 hours ago, Don Pensack said:

A 21mm eye lens and 60° field translates to an eye relief of 18.2mm on the Starguiders.

It could be 16mm from the edge of the lens out if the eye lens is strongly concave, but I don't recall that is the case with the Starguiders.

That might explain why many people can use them wearing glasses.

Due to a couple of different eye lens sizes and 3mm to 4mm eye lens recession due to the eye cup design, I measured the usable eye reliefs as below:

The AstroTech Paradigm is the same as the BST Starguider.  The discontinued Meade HD-60 line is much more eyeglass friendly across the line.

My thoughts on the two lines are in the following thread:

While the image loaded, I thought you were going with this to explain the planet-wide smog of Venus:

If we assume the eyepiece has a 46.5mm field stop and the scope has a 303mm focal length, the TFOV = 46.5/303*57.2958 = 8.79 degrees.  The actual AFOV is irrelevant and highly dependent on various distortions.  It only affects the presentation of the TFOV to the eye.

You might look into the new Svbony 3-8mm zoom.  It's been getting good initial reviews on CN, has a 60 degree AFOV, and comfortable eye relief.

Avoid the Panorama II and Meade MWA lines.  Both closer to 80 to 90 degrees in AFOV and suffer from significant SAEP (kidney-beaning).

Don't overlook the other 100 degree variants on the APM XWA line.  Astronomics has their Astro-Tech 100° line in the US, and then there's the Stellarvue Optimus line in the UK.  There are more brandings out there, but I can't remember their names offhand.  Eye relief in the shorter focal lengths will be much better than in your 6mm.

I've owned a Short Tube 80 as they used to be known for over 20 years.  It rarely gets any use due to spherical aberration decreasing contrast and sharpness.  My sharpest views with it are with a light green filter to cut out the red and blue ends of the spectrum where the light isn't focused very well.  It turned me off to refractors for years.  Then, about a decade ago, I bought a 72mm ED refractor and absolutely love it.  Very sharp optics and practically no false color.

While stars aren't as crisp in a parabolic mirror Newtonian as in an APO refractor, they're definitely better than in an unfiltered ST80.  You can also resolve DSOs more easily in a 130mm Newtonian.

I bring the ST80 on road trips as for the 2017 solar eclipse because I don't really care if it gets stolen from my car.  That's how little I think of it.

Avoid fungus.  It can spread to other optics once in your home.  The problem only gets worse as the fungus spreads within the lens.

Minor scratches at the edge might not affect the image.  Avoid them across the center.  Avoid the lens if it looks to have been sandblasted (used near beaches, waterfalls, etc.).

A basic, manual 50mm f/1.4 to f/1.8 lens from years ago can be a good starting point for very little outlay.  Autofocus doesn't buy you much if anything in astrophotography.

I was referring to kit #2:

2) Kit with OTA only (1-speed focuser) $328

That seems high by 2005 standards for a fast achromat with a single speed 2" focuser.  Generic ST80s were going for about $100 or so with a 1.25" single speed focuser.  I can't imagine a 2" single speed focuser added $228 to the price.  When I started reading the review, I had assumed it had ED glass to account for that price increase.

Wow, that scope seems to have been massively overpriced for an 80mm f/6 achromat with single speed 2" focuser by 2019 pricing standards.  I would have thought it would have had ED glass for that price.

Sounds a bit like the Tele Vue Bizarro, except that it was an 85mm scope.

The best page for comparing eyepiece types on TelescopeOptics.net is 12.4. TELESCOPE EYEPIECES: COMPARATIVE RAYTRACING.

Two other eyepiece diagram charts floating around the web for years are below:

You can see that the Achromatic Ramsden is indeed very similar to the Kellner in design.

The definitive optics book for amateur astronomers is Telescope Optics : A Comprehensive Manual for Amateur Astronomers by Harrie G. J. Rutten and Martin A. M. Van Venrooij.  I find myself going back to my copy every so often to reread certain sections.

1 hour ago, imakebeer said:

Thanks 👍 Any idea what LET actually stands for by the way? I wear glasses but I can't immediately see how the twist up eyecup helps, early days yet though.

Actually, it helps if you don't wear eyeglasses at the eyepiece.  It twists upward to reduce usable eye relief to place the eye at the correct distance to avoid blackouts.

I've always presumed the LE of LET stands for Long Eye (relief).  Maybe relief starts with a T in some other language?  There are multiple long eye relief eyepiece lines labelled as or with LER, but this is the only one using LET.

1 hour ago, Highburymark said:

Nice set up Robert!
I love widefield views with small refractors. Don’t have a 2” diagonal anymore, just T2 prisms and mirrors - but still see sharp field stop with 60ED/APM 100 degree 20mm and Panoptic 27mm, my only two 2” eyepieces.

Which end do you look in? 😁

For balance with heavy 2" eyepieces in my 72ED, I have to clamp the dovetail bar almost directly under the focuser knobs, so the scope is cantilevered on a long bar.  The other problem I have is the focuser slips under the 3+ pound 2" load despite cranking up the focuser default tension screw under the pinion and roughing up the flat of the focuser tube.

I've had jamming issues when the focuser compression ring rises out of its channel and gets jammed against the undercut on an eyepiece.  I've only ever used smooth sided focuser plugs in storage, so no issues there.  In fact, they've always been made of flexible plastic.

Perhaps posting a picture of what's jammed where might help.

Here's a much more recent thread covering multi-finder setups:

Following Star Hunter's lead, I bought one of the cheap spectrometers off of ebay and have been modifying it to image filter spectra.  I'm still getting the hang of it, but I composited several of my line filters together with an image from Star Hunter to show the relative passbands of several line filters together.  I may not have got the scaling or alignment quite right, but it's close.

My 1990s vintage Lumicon UHC is considerably narrower than the Svbony UHC.

My 1990s vintage Lumicon OIII leaks a lot of red light, more than the Lumicon UHC!  At least it hasn't rusted.

The Zhumell OIII doesn't leak any red light at all!

The Lumicon OIII in my observing experience and the test sticker on the filter case indicate it is well centered on the OIII lines.

The Zhumell OIII is well to the right, more in the Swan bands (Carbon) than the OIII bands.  I'll have to try this filter on comets in the future.

The two OIII's stacked indicate a bit of overlap, so maybe the Zhumell passes at least one of the OIII lines?

The Zhumell Moon & Skyglow (M&SG) is basically the same as Baader's Neodymium filter at a far lower price (between $10 and $15 about a decade ago).

The M&SG probably increases contrast by separating the overlap of the red and green and to a lesser extent green and blue parts of the spectrum.

However, only the 18mm ES-82  and 24mm and 40mm ES-68 eyepieces show as in stock at FLO.  At least here in the US, I've read of people waiting 9 months to several years for certain focal lengths to come back in stock.

It appears that your text got cut off before the binoviewer (turret) experience could be described.  Perhaps a google translate artifact?

Sounds like cross importing ES from UK/Europe to the US is the way to go for us if that's what we want/need.

Definitely no import tariffs or other tax issues from abroad, new or used, under the $800 de minimis exemption.  It is great for small items because you bypass the 25% special tariff and state and local sales taxes that generally more than pay for shipping fees from many retailers.  Some retailers do insist on using super expensive 3 day or less shipping options, so you have to watch out.

The ES 68/82 lines used to be a great deal when they came out, then they jacked up the prices to very close to Tele Vue prices.  For instance, the 40mm ES-68 is $519 while the 41mm Panoptic is $576.

On 19/02/2010 at 12:04, mint_mark said:

Good question. I discussed it with a friend and we came to the conclusion that the circles are projected up onto the window from below in a diverging beam of light. They reflect off the angled window towards your eye, but they are still diverging... so the further back you are the further apart the rays are and the larger the circles look.

If the circles were a constant size then the finder would only work (cover 2 degrees) at a fixed distance from your eye.

Roughly speaking, the circle is projected, so it appears to float at infinity to avoid parallax issues.  The Telrad actually achieves this while the QuikFinder falls a bit short of infinity projection and has a bit of parallax if you shift your head off center.  Said another way, the red circles don't stay perfectly positioned on the sky like in the Telrad.