Louis D

Did you try putting the Barlow into the wedge?  It's too bad the threads on the TV Barlow nosepiece aren't 1.25" filter threaded, then you could dispense with the long Barlow barrel and definitely reach focus.

Why the long train of step down adapters (three by my count) on the back of the focuser?  If it did the step down in one low profile go, I'm sure you could reach focus.

I use the nosepiece of a vintage Meade 140 2x Barlow on my Arcturus BV to reach focus even in my Dob which has only 20mm of in-focus left.  It operates at 3x in that configuration.  Check the astro classifieds and maybe put out a wanted ad.  There are some other screw in Barlow/OCA/OCS/GPC options out there as well to help reach focus.

4 hours ago, F15Rules said:

I agree with Jock, an Ultrashort clamp and Baader T2 prism gives you the best chance to get focus without a Barlow lens. 

No applicable for Herschel wedge usage.

Dust has to be really heavy before it affects the views in any appreciable manner.  You can stick your hand in front of a large Dob's opening while observing, and the most disruptive effect will be from the heat waves shimmering off your hand in cold weather, not the actual blockage.

Overzealous cleaning of optics can lead to micro-scratches that will affect contrast by increasing light scattering.  It's generally best to leave light dust evenly coating a mirror or corrector plate rather than trying to clean it off.

If your Dob is balanced to handle 30mm 82 degree, 40mm 68 degree and 17mm 92 degree eyepieces that each weigh over 2 pounds plus a coma corrector, you'll do fine with a binoviewer loaded with a Barlow/OCS/OCA/GPC nosepiece and two compact 15mm to 20mm eyepieces that your nose will fit between.  I find that at 3x with the 2x Meade 140 Barlow nosepiece in my BV, I don't use my GSO coma corrector because it just adds axial spherical aberration without noticeably improving the edges.  This lightens the load on focuser a bit.

At an effective f/18, I find the SVBONY 68° Ultra Wide Angle 20mm eyepieces to work great:

I would get the 40mm ES-68 if you want to absolutely maximize your possible true field of view.  It is the same optically as my 40mm Meade 5000 SWA.  There is just a bit of astigmatism in the outer field of view.  If you want absolute perfection, then the 41mm Panoptic is the way to go.  The difference in price is only $56 here in the US.

A lower cost alternative is the 40mm Pentax XW-R which has just a tiny bit more true field of view, a bit of field curvature (not visible to those with younger eyes that still focus properly), and a bit of edge astigmatism.  It's $120 cheaper than the 40mm ES-68 here in the US.  It's also considerably lighter.

Stars will be a mess in the outer 25% of the field of view without a coma corrector at f/5 regardless of eyepiece.  You would see a massive improvement with just the GSO/StellaLyra CC and a 25mm M48 spacer ring.  It's been good enough visually for me that I've not felt the need to get a Paracorr II.

It's much easier to take in a 68/70 degree field of view all at once than an 82+ degree presentation.  It's hard to appreciate what is going on in the periphery once you get past 70 degrees without looking directly at it.

At f/5, the exit pupil is going to be getting a bit large with a 40mm (40mm/5=8mm), so the sky will be somewhat washed out.  This isn't a bit deal with bright star clusters like the Pleiades, but the hazy nebula within it will be hard to detect.  You'd be better off with a smaller scope and smaller exit pupil to observe the dusty nebula around the stars to darken the sky background a bit.  You could always bump up to a 20mm to 30mm eyepiece in your f/5 scope to darken the sky background and observe parts of the dusty nebula in sequence rather than all at once.

At f/5, a 30mm eyepiece provides a 30mm/5=6mm exit pupil, which is much better, but still overly large.  The background sky will still be somewhat bright.  Personally, I prefer the somewhat washed out sky and easier to take in view of the 40mm eyepiece over the 30mm eyepiece.

Another option are the various 20mm 100 degree eyepieces out there.  There's the APM, Myriad, Astro Tech versions which are lighter, lower priced, and better performing than the ES-100 variant.  You lose some true field of view while massively darkening the sky (20mm/5=4mm exit pupil).  However, eye relief is tight and it is impossible to see the edge sharply without rotating your view way off axis.

There's no magic bullet here short of mounting a smaller scope to your f/5 scope for wider true fields of view.

In the 30mm ES-82, the outer 10% has CAEP, chromatic aberration of the exit pupil.  The red and blue ends of the spectrum focus above and below the average exit pupil distance.  The effect is to impart a color cast at the edge.  At night, you can't see it unless you move the moon or a planet out there.  A neutral colored planet like Jupiter splits into distinct red and blue images.  Each is fairly sharp, but they do not coincide in the field of view in my experience.  If you strictly keep objects centered and only look on axis, you will never notice this.  However, if you have an undriven mount and let objects drift from edge to edge, you will see it.

The field of view is very flat and sharp, it just has these slight issues at the outer part of the field.  That, and there is a bit of astigmatism out there, but it is relatively minor.

What's your budget and what are you hoping to view with any of these eyepieces and with what telescope?

Do you need to wear eyeglasses or not at the eyepiece due to astigmatism?  I prefer my 30mm APM over my 30mm ES-82 and 27mm Panoptic due to much better eye relief.  That, and the APM is sharp edge to edge at f/6 with no ring of fire like the ES-82.  The ES-82 gives a more immersive experience, but is tiring to use unless you pull back to the same field as the APM.

The 35mm TV Pan has been produced in two versions, one with a recessed eye lens, and one that's closer to flush mounted.  If you buy used, make sure to inquire which type it is.  Those who don't wear eyeglasses prefer recessed while those who do prefer flush mounted.  I've used the 35mm Pan at star parties, and find it very well corrected and usable with eyeglasses if flush mounted.

I prefer my 40mm Meade 5000 SWA or 40mm Pentax XW for widest field views.  At 35mm, my favorite is the discontinued Baader Scopos Extreme.  It is quite usable with eyeglasses and extremely sharp in the inner 60% of the field, and just barely falling off in sharpness to the edge.

Thanks guys.  Makes total sense.  I forgot about the lack of IR filtering and high IR sensitivity on those cameras.

I have an old Olympus C-2000 that I use with an R72 filter for poor man's IR photography.  It was the last (or nearly so) Olympus digital camera without an IR-cut filter ahead of the sensor.  It's so sensitive to IR, I can use normal shutter speeds to photograph objects and people without motion blur.

I hope this isn't a stupid question, but why does the no filter image have the most color shift of the four images (I see it as pink on my monitor)?  Did you use a weird color balance on your camera for all four images, and it balances out the color shift of the filters on the other three but ruins it for the no-filter one?  It just seems counter intuitive that the filtered images are more neutral than the unfiltered image.

On 13/04/2022 at 08:35, Franklin said:

Finally got round to casing up my collection of Vixen eyepieces and taming my OCD for a while.

 

I'm glad to see the LV/LVWs in there to complete the collection.  Very nice indeed.

Is there a reason you're averse to using a 1.25" to T2 nosepiece adapter?  There's one one ebay UK for £7.99+S/H:

Are you super concerned about edge vignetting or image train tip/tilt/sag to want it integrated into the Barlow?

4 hours ago, russ said:

First instrument was a pair of Swift 10x50 binoculars. I wanted a telescope but Mum used to watch Sky at Night and Patrick said you should start with binoculars. Never been so gutted EVER. Of course I had to look grateful and I did give them a go. Thought they were a waste of time and tossed them in a draw. Six months later I was bought a 50mm Tasco refractor. And from that point on I was hooked. One look at Saturn, job done. I wrote to Patrick to tell him how badly wrong his advice was. I was only 14 at the time. And cringed later when I realised what I had done. And Patrick being the awesome person he is wrote back with a diplomatic reply.

Still have the Swift binoculars, a prized possession now. A few years later I realised the worth of binoculars and also how good Swift were. I stand by what I told Patrick though, binoculars are definitely NOT the right choice for everyone. Had it not been for that little Tasco I wouldn't have been hooked.

Right there with you.  Other than looking at large star clusters/fields, they aren't all that useful.  Everything is jumping about because your own jitters are being amplified 6x to 15x, so you can't see anything but the brightest stars and planets/moon.  If you're going to put the binoculars on a tripod, you might as well put a telescope on there.  The viewing angle will be much more comfortable unless you bought a dedicated pair of astro bins with 90 degree prisms for $1000+.  At that point, why not just buy a telescope?  I had bins for years, but it took a telescope to really get me going on amateur astronomy in my 30s.

Maybe a nice used 12" to 15" custom truss Dob.  They come up used on American astro classifieds for a fraction of new price all the time.  As long as you're willing to drive part way to pick-up, they're a good deal.

Talk it over with @Olli who just went with a Sky-Watcher SkyMax-127 AZ GTi after starting the below thread trying to replace a Dob:

5 hours ago, Alan White said:

Indeed a serious subject for many, torture for some.

My real concern about the Oscars, is who gets slapped!

Beat me to it. 🤪

2 hours ago, Stephen Waldee said:

For a while, for easiest use in my permanent backyard C-11 observatory building, I kept the eyepieces in a box inside, with the scope...until one hot day in Utah, USA summer, the rubber eye cup on a particular eyepiece 'melted'.  So I gave up on that and put them all in the four pluck-foam travel cases and store them inside in an air conditioned room!

I could see this being a problem in Texas as well.  We hit 112° F in 2011 and had a total of 90 days above 100° F that same year.  It was brutal.

In the US, Southwest Airlines still allows two free checked bags and one free overhead bin carry-on bag.  All other US carriers charge for checked luggage and the low cost carriers also charge for overhead bin carry-ons.  If you do the math and need two checked bags and a bin-sized carry-on, Southwest is generally the way to go for domestic flights.

1 hour ago, Ricochet said:

Aren't the HD-60s supposed to be the same eyepiece as the Celestron X-Cel LX internally? I had the 7mm X-Cel LX and remember it as being a very good eyepiece. In a way it is a shame that I sold it as it would have been good to reassess it now I'm a much more experienced observer.

Since I've never used the Celestrons, I cannot confirm that.  However, there is a strong possibility they are related making the 7mm and 9mm basically the same.  I just like the adjustable eyecup design on the Meades better, so I bought a set of them for comparison to the BST Starguiders (Paradigms).  Those two focal lengths were noticeably better in head to head comparison with the 5mm and 8mm BSTs.

5 hours ago, doublevodka said:

Obviously you'll need a bigger bowl for the larger mirror, but you get the idea

I've read that the big Dob guys scrub down their bathtub and then line it with towels before partially filling it with detergent water to give their big primaries a good soaking.  The towels protect both the tub lining and the mirror from each other.

Generally, prism diagonals have a shorter optical path length (OPL) than mirror diagonals of the same clear aperture.  IIRC, A 90° Amici prism diagonal should have the same OPL as a plain 90° diagonal.  A 45° prism diagonal may have a longer OPL because they use a Schmidt prism, IIRC.  Which type(s) of correct image diagonals were your using during your testing?

Vixen SLVs are $175 before tax from most reputable retailers here in the US.  You can get used Pentax XLs for that money quite regularly.

I forgot to mention used Vixen LVs.  They generally go for under $75 each on the astro classifieds here in the US.  They view like Pentax XLs/XWs, just narrower in field of view.  They should perform excellently at f/4.7.  I've had my 9mm version for 25 years.

3 minutes ago, Carbon Brush said:

On theft from luggage. I always secure zips and locks using small cable ties through the loops.
Easy enough to cut for a genuine security check or for theft. But I will know immediately (at the collection carousel) if someone has been in there.
 

They just put a new zip-tie on it when done to avoid attracting attention.  Legitimate checked baggage inspection does the same and puts a note in the bag informing you.

If you can find used copies of the discontinued 9mm and 6.5mm Meade 5000 HD-60 eyepieces, they are real gems that perform very close to Pentax XL/XW and Morpheus levels at f/6.  They were under $100 each when new.  They're also quite usable with eyeglasses.  They should still perform well at f/4.7, but I can't confirm that as I don't have a scope that fast.

If eye relief isn't an issue, there are a whole lot of options out there; but many, like the Abbe Orthoscopic suffer a bit at f/4.7.

7 minutes ago, Philip R said:

The tripod, mount, 2x SLR’s, photo lenses, 6x rolls of 35mm film, photography bag, etc., went in the suitcase, protected by my clothes.

You're lucky they didn't disappear in baggage handling.  Theft from checked baggage is a big issue in major US airports.  The X-ray machines show them exactly what's inside, so they alert an accomplice to do the dirty work later in handling.