Louis D

1 hour ago, johnturley said:

I don't usually use a coma corrector with my f5 Newtonian, although I do have an Explore Scientific HR Coma Corrector, no doubt the results would be better if I used it, as I tried once with my Baader 36 mm Hyperion Aspheric, and it gave improved results.

1 hour ago, johnturley said:

Agree, I find that with the StellaLyra 30mm UFF in my f5 Newtonian, stars at the edge of the field are not in as sharp focus as those in the centre, not that they suffer from coma, but can be re-focused.

Give the ES HR CC a try with the 30mm UFF sometime, and see if both issues are minimized.  Most CCs not only correct coma, they also help to flatten the field.

If you can live with both issues, and the imbalance issues with the CC outweighs the sharpening effects, then definitely continue using the UFF straight into the focuser.

You don't say which coma corrector you were using with your f/5 Newtonian.  I've found my 30mm APM UFF to be sharp to the edge with a GSO CC in my f/6 Dob.

I've measured its AFOV to be 73 degrees.  It's eAFOV (to plug into TFOV calculators) is indeed 70 degrees due to slight distortion.

52 minutes ago, Ratlet said:

I phoned the wife to get the scope up the shed to cool as this might be the last clear night for a while.  Been working since 0600 this morning and got home at 1900 but oh boy, was it worth it.

Over on the svbony 3-8mm zoom post @Louis D suggested I order a cheap yellow and moonglow filter from eBay to improve contrast on Jupiter and mars.  Total cost was £10.  They both turned up today so I went out to excellent seeing getting straight to 3mm with the svbony for 216x power.  Jupiter looked very steady without the filters.  With them it just looked astounding.  Amazing detail and it almost made the atmosphere look even more steady.  It almost looked photographic and the colour cast was most pleasing.  I couldn't dwell for long before moving to mars as I need to go to bed shortly.

WIt's the filters Mars was hands down, no contest the best view I've had.  I could see definition to the light and dark areas so clearly.  I would swear on my life I could see a distinct white area on the north limb.  It felt a lot more like I was looking at an object where as previously it was like looking at a light, if that makes sense.

I tried without the stacked filters and whilst the viewing was good, the atmosphere seemed more unsteady and the light darker areas were more blurred.  I'm not confident I could see any white at the north again.

I'm certain that the seeing helped massively but for £10 I've had the best views of mars and Jupiter I've had.  The previous best coming because I bought the svbony zoom based on @Louis D review of it!

I've linked the filters I bought below.

https://stargazerslounge.com/topic/399997-svbony-8-3-zoom/page/5/#comment-4334138

Glad those filters worked out for you.

I've been experimenting with various yellow filters trying better understand what density of yellow is needed to suppress unfocused violet light in my 80mm f/5 refractor.  So far, it appears that lighter is better on less bright objects, but brighter objects require a denser yellow.  I think it's because our eyes simply can't perceive dim, unfocused violet; but can when it becomes brighter.  That yellow filter you bought should be just about appropriate for planets in fast achromats without introducing a noticeable yellow cast.  I think it's close to a Yellow #8.

Let us know what you think of it once you get a few nights use out of it.

I believe the GSO has a 75mm +/-5mm separation requirement.  So, if you're roughly in the ballpark, you're good to go.  Since most of my eyepieces focus within 5mm of the shoulder, I've found that adding a 25mm M48 spacer ring between the optics section and the eyepiece holder removes 95%+ of all visual coma for nearly all of my eyepieces.  The lone exception is my 12mm Nagler T4 which focuses 20mm below the shoulder.  I could clearly see residual coma, so I did the following to parfocalize it using five 4mm-thick, 48mm-ID O-rings and a 20mm M48 extension tube:

I say visual coma because a camera would most likely still detect some uncorrected coma, but our eyes are not so adept at noticing slight ovalness to stars in the far outer field.

The Tele Vue Paracorr II and ES HR CC both have tunable tops, but I think their designs are less forgiving of being off a few mm from the correct spacing.  That, or their owners are less forgiving of slight imperfections.

I will warn you to remove the pot metal thumbscrews GSO supplies with their CC and replace them with M4 steel cap head hex screws.  One of their cheapo screws sheared off in one of the two thumbscrew holes and I can't remove the remnants without drilling it out and retapping the threads, so I've been living with using a single steel thumbscrew since then.  Why do they do that?  A dozen steel screws bought in bulk would probably cost no more than a dollar in Taiwan.

Here's a nice thread on CN about these Vixen made short tube 80s.  Seems like you picked up a vintage winner.

Coma is one of those things that you don't notice until it's gone, and then you notice it when it's back.

I went without a CC for 15 years in my Dob quite happily.  Then, a GSO CC came up for sale on CN classifieds for $75, so I went for it since it was a fraction of what I was paying for individual eyepieces during that period of upgrading.  BOOM!  The outer regions of 70+ degree eyepieces were noticeably sharper.  When I removed it, I couldn't unsee the slight unsharpness I had been living with.

Admittedly, if your eyepieces have loads of astigmatism or field curvature in the outer field, you won't notice a difference.  This was the case for me prior to my eyepiece upgrading spree.  You also might not notice with long eye relief eyepieces with powerful Smyth lenses that slow down the incoming light cone for the image forming upper group(s).  This is the case with my 10mm Delos.  I absolutely cannot detect any change in the image with or without a CC.  This is not the case with the 12mm ES-92, however.  It desperately needs a CC for best performance.

Low power eyepieces like Panoptics and their clones probably benefit the most from a CC.  I've also found that some long focal length eyepieces have sharper field stops with the CC than without.  I have never been able to pinpoint what is the optical cause of that artifact.

I use a GSO coma corrector with a 25mm spacer tube between the optics nosepiece and the eyepiece holder.  With my ES-92 eyepieces, it's quite obvious even at f/6 when I forget to put the CC in the focuser.  However, at high powers, I have to remove it because it induces a bit of spherical aberration on axis which turns fine planetary details to mush.  The Tele Vue Paracorr II reported doesn't have this issue.

14 minutes ago, fwm891 said:

Take a look at the Altair astro refractors 

Are you referring to these offerings?

Altair 70 EDQ-R F5 Quad APO Astrograph

TS-Optics 70 mm f/5 Quadruplet Flatfield Apo with 3-Element FPL53 Objective

TS-Optics 61EDPH - 6-Element Flatfield Apo 61 mm Aperture F/4.5

TS-Optics 5-Element Flatfield Photo Apo Refractor - ED61PHD

I picked up the Svbony UHC since it's already wider in passband than a typical premium UHC, so it's closer to a light pollution filter already.  The CLS is getting too wide to be of much use at all.

28 minutes ago, michael.h.f.wilkinson said:

If they did that, the mighty Nagler 31T5 "Panzerfaust" would likely go. That is one of my most used EPs, I must add. Really love it in the C8, but in the Meade SN-6 6" F/5 Schmidt-Newton and the APM 80mm F/6 triplet, it really comes into its own regarding wide-field viewing.

The usable eye relief of the original mushroom top 30mm ES-82, which is slightly better than the 31mm NT5, is just too tight to be comfortable panning around with eyeglasses.  Both have about a 30mm diameter eye lens, which is simply not enough for an 82 degree field to be comfortable to use with eyeglasses.  It's doable, but not easy.

Here's a size comparison of my 29mm ES-92 (labelled 12 obviously) with my decloaked 30mm ES-82 and 40mm Pentax XW-R:

I don't use the 29mm ES-92 regularly, but instead break it out occasionally to liven things up a bit.

4 hours ago, michael.h.f.wilkinson said:

Just read the comparison of the XW 23mm to the Nagler 22 T4 on CN, and the Nagler is safe in its place in the EP case (until ES decide to do a 22 mm 92 deg)

Right there with you.  Your eyepiece journey with the NT4s and ES-92s exactly mirrors mine.

I do have the 29mm ES-92 unicorn eyepiece.  It started out as a 12mm ES-92 missing its field (Smyth) lenses that ES sold in a large lot of warranty returns.  I've always wondered how it got in that condition.  I pieced together a couple of hard-to-find step rings to reduce its in-focus requirements from 40mm to 21mm.  If I screw my GSO CC nose piece directly into the filter threads, I can reach focus even in my Dob.

It has a lot of chromatic aberration starting not far off axis, but if you look straight at the center, it's not that noticeable.  Its much better than the vintage 30mm Kasai Super WideView 90° in this regard.  The measured AFOV remains at 93° as with the original 12mm ES-92.

It is remarkably free of edge astigmatism despite lacking its Smyth lenses.  Usable eye relief remains about the same as for the original 12mm ES-92 which I also have.  The measured field stop using photography is 48.4mm despite measuring 51mm with calipers.  The FS being well above the top of the 2" barrel allows for this.  The internal field stop is now fully accessible for direct measurement  just like in a Panoptic.

It is a hoot to pan around star fields with.  The window into space effect is full blown.  Without the Smyth lenses, there is no SAEP (kidney-beaning) at all, so holding the view is a breeze while panning, even with eyeglasses.  I've compared it to my 30mm ES-82, 30mm APM UFF, 30mm Widescan III clone, 26mm Meade MWA, 29mm Rini MPL, and the 30mm Kasai SWV 90°; and it is in a league of its own for low power, wide field panning with eyeglasses.

If ES would offer this as a product with some sort of chromatic aberration corrector instead of the Smyth lenses, it would sell like hotcakes.

12 minutes ago, HollyHound said:

I have the Masuyama 16 and 26 and they are both superb for clarity, contrast and colour and they're also very lightweight... they have the same FoV as the new XWs though, so for that reason only, I may be moving one or both of those on, and settle on a full set of XWs (3.5, 5, 7, 10, 16.5, 23 and 40). I have reached the stage now where I want one choice for a given focal length in my main set (keeping another small set for grab and go or travel) 

It seems like you'd want to keep the Masuyamas for the lightweight set given how big and heavy the new XW-85s are.

I've gotten a couple of new filters (Lumicon's second most recent OIII that they're clearing out for $30 with their MOVINGSALE2023 code and the Svbony UHC), but no time at night to try them out yet.  I imaged their spectra through my spectrograph and came up with the following:

The Lumicon UHC and OIII Old both date to the late 90s.

The Zhumell barely does anything for OIII being too far right of the lines, but might work as a comet filter and the C lines.

The new Lumicon leaks an unnoticeable bit of red, so a major improvement over my vintage filter.  In fact, the vintage Lumicon OIII is more of UHC with no H-beta line.

The Svbony UHC is more of a light pollution filter than a true UHC filter.  It might also make a decent magenta filter on Mars.

I hope to try them all out on the Orion nebula in the near future.

I use the nosepiece of a vintage Meade 140 2x Barlow which operates at 3x in my Arcturus binoviewer to reach focus in all of my scopes.  My Dob is setup with maybe 25mm to 30mm of in-focus from its focus point.  The Meade nosepiece results in very sharp views.

4 hours ago, Chaz2b said:

how many cameras do you have

Way too many non-astro cameras.  Most aren't worth selling because they're hopelessly obsolete.  I have donated a few to my son's friend who likes photography, but is a college student without spare cash.

I've had zero issues direct importing from the UK or anywhere else in Europe or Australia.  No sales taxes, no import duties, no customs hold-ups ever.  The only issue I've had is checkout carts that refuse to remove VAT prior to payment.  I refuse to take any retailer's word that they'll credit erroneously paid VAT back to my CC.

I'm guessing direct importation into the US is such a small fraction of all importation that it's just not worth creating a bureaucracy to collect the lost revenue and stall free trade.  The main things they do check for are illegal drugs, weapons, and explosives.  Even then, literally tons of fentanyl from China gets through every year to be resold on the streets as mismarked pain relief pills.

On 14/01/2023 at 08:09, Mr Spock said:

Can everyone steer clear of the 'B' word please.

Belgium?  The most unspeakably rude word in the universe according to the Hitchhikers Guide to the Galaxy? 😁

It could be you don't have enough in travel or out travel to reach focus with the fully inserted Barlow lens.  Try this first.  Bring an object to focus with the eyepiece alone and lock the focuser.  Next, put the eyepiece in the Barlow.  Now, slide the Barlow/eyepiece combination into the focuser slowly while observing the object through the eyepiece.  Does the object come to focus before the Barlow is fully inserted in the focuser?  If so, you may not have enough out travel to use the Barlow fully inserted.  If that is the case, simply partially insert the Barlow and tighten it down.  There's no harm in using it this way.  If on the other hand you inserted the Barlow all the way and the image never reached focus (got smaller and smaller and then you ran out of travel) even after loosening the focuser tube, then you don't have enough in travel to use the Barlow, period.  Try finding a longer Barlow since they tend to require out focus relative to the eyepiece alone focus position and sell the Barlow you already have.

@Mr SpockWould it be possible to change the title to include johninderby and Rest In Peace or equivalent to make this more prominent?  He will indeed be missed and has already been missed during discussions on SGL.  Thanks.

Same 27mm field stop as a 32mm Plossl or 24mm APM UFF, just with a narrower apparent field of view because the same image circle is presented at a smaller image scale due to the lower power.

Why not just redesign your scope to be compatible with 2" eyepieces if you want a wider field of view?

If you have enough in-focus, it is possible to put a larger than 27mm field stop above the insertion barrel, but you will have some edge of field vignetting.  The vintage 35mm Celestron Ultima took this approach.

I've also held my 27mm Panoptic's 2" insertion barrel around the 1.25" receiver barrel with the thumbscrew removed, and it worked quite well visually.

1 hour ago, kdahl said:

You are absolutely correct sir. It says CPL on it. What is the big difference? I can really only find compares between UHD and CLS. Thanks!

Svbony has this blurb on that linked ad for the CPL filter:

CPL filter is mainly used for elimination of polarized; and enhances the contrast of the moon and planets in photographic images

Visually, I can't think of any use for a CPL filter in astronomy.  A variable polarizing filter is handy to vary the brightness of objects.  This can be useful for the moon, Jupiter, Mars, and Venus.  However, these filters are actually two linear polarizers back-to-back with a swivel attachment between them.

A CPL or circular polarizer is used in photography to cut through polarized reflections such as from a glass or water surface to image what lies beyond.  The circular part returns the light to being non-polarized after passing through the linear polarizer part, thus they can only be used in one orientation, linear polarizer facing the object.  This circular step is needed because polarized light really messes with light sensors inside the camera that are sensitive to polarized light.

Svbony should have just included a tradition neutral density moon filter instead.  These cut the brightness of objects by a fixed amount (generally 13% transmission or 87% attenuation) without changing the color balance.

Here's a composite of images I took through my spectrograph of various filter combinations to give you some idea of what's possible with filter stacking:

Figure that a Yellow #8 is going to be similar to the Yellow #12A which is currently unavailable new.

Meade was purchased by Ningbo Sunny in 2013.  Ningbo Sunny purportedly has close ownership ties with Synta, but this has never been proven.  After the anti-trust lawsuit between Orion and Ningbo Sunny was settled, Orion ended up with ownership of Meade.