Louis D

1 hour ago, Astro74 said:

Any suggestions for the option 1 ? 

Here's the Datyson Moon & Skyglow from ebay for under 3 GBP.  How wrong can you go for that money?

Howdy from Texas.

I've always meant to ask, how long do you spend each year updating it?

Option one would be a generic Moon & Sky Glow (Urban Sky) filter which are pretty close to the same as the BN at a fraction of the price.  This will cut yellow and orange completely and dim some green.

Option two would be a Svbony CLS filter.  It completely cuts all light from green to orange leaving only blue and red.  It's like using a hammer to drive a tack, though.

Option three would be a Svbony UHC filter.  It's a bit narrower in the blue and red parts of the spectrum increasing contrast on nebula even further than the CLS.

Take a look at this post of mine about LP filters from a couple of months ago.

Here's some various filter spectral images from Star Hunter and myself to see what gets cut and what remains.

The Baader Scopos Extreme 35mm is quite sharp at f/6 edge to edge, and sublimely sharp in the inner 50%.  It has tighter stars there than many of my premium wide fields.  The downside to it is how big and heavy it is.  Weight wise, it slots between my 12mm and 17mm ES92s.  As such, I don't need to rebalance my scope when switching among these three eyepieces.

Here is Jon Isaacs's mini-review of it on CN.  He is an incredibly experienced observer, so I trust his take on it.

I have the 35mm Aero ED, and it is sharp at f/6 out to 75% of the field.  At f/8, either eyepiece would probably perform quite well.

Adding the CLS filter all the time could be very detrimental for planetary viewing where light pollution doesn't matter much at all, but the cut out wavelengths (green through orange) could have conveyed a lot of detail.

For starters, try reading this CN thread on Kitakaru eyepieces from other retailers in the past.  That's about all I know of them.

The problem with these budget scopes isn't so much the objectives, which can be quite good, it's the rest of the system.  They may have plastic focusers, plastic body diagonals, internal aperture stops, and wobbly mounts.

I would contact and work with Tejraj & Co. which is sort of the FLO of India.  They are a long standing, legitimate Indian astronomy retailer who should be able to answer your questions and find something within your budget.  If you need help post-sale, they'll be there to help.  Look at their house brand Star Tracker telescopes.  There are several sub-15,000INR options available.  It's best to support these dedicated astronomy retailers because they have been disappearing around the globe over the last 20 years with few replacements.

No stacking is possible unless you pair it in front of a thicker filter with front female threads.  Don't remove the retaining ring unless you do it indoors over a cushioned surface in case the filter material drops out.  There's no guarantee that the revealed female threads are even 1.25" filter compatible.  If they are, and the stacked filter has long enough male threads to securely hold the filter material in place, you might get away with a fixed stack that night.  I would be hesitant to swap the stacked filter in the field in the dark for fear of losing the back filter material.

As a workaround, try attaching one to the filter threads of the eyepiece and hold the other between your eye and the eyepiece to quickly try different stacks to see which might be worth pursuing via other brands for one of the two filters.

Another option would be to put one filter on the front of the diagonal and one on the eyepiece if not using a Newtonian telescope.

On the plus side, they're lower profile, so they may fit in some filter wheels better.

They are also cheap relative to GSO made filters which do have front and rear threads.  These Svbony filters are also way cheaper than Baader, Lumicon, and Brandon color filters.

Give them a try.  What's the harm?  Worst case you confirm your impression of them.

17 minutes ago, stormioV said:

I  have Starguider/Arcturus Binoviewer and use pairs of 8mm, 18mms & 25mm BST Statguiders. 18mm are my favourite. I also have the x 1.85 & x3  Barlow that were included in set. I'm not against getting another 12 & 15. Would orthos be a better way to go for BV?

Lightweight zooms are very handy I've found to avoid swapping two eyepieces while making sure neither is tipped in the holders.  It makes for a more relaxing viewing experience.

How about a beauty shot of all of them out of their boxes.  For all we know, you bought a bunch of empty boxes. 😄

Ask yourself where do you find yourself lacking in focal length options?  Also ask yourself where you'd like a wider apparent (and true) field of view at a particular focal length.

You're already pretty well covered for monoviewing.  I'm not sure what eyepiece pairs and GPC/OCA/Barlow elements you're using with your binoviewer.

I've had my ST80 since about 2000.  Since it was such a poor performer relative to my Dobs, I was very dismissive of it and relegated it to travel use as a spotting scope or white light solar scope (as during the 2017 eclipse).  I tried that Minus Violet filter shown in my post above and found it did so little to cut stray violet light that I abandoned experimenting with filters to improve the image in the ST80.  Now I've circled back to see if the right filters with just the right cutoff characteristics could make these achromats more palatable to reflector folks like myself.

@RatletI predict that someday in the next 5 years you'll pop for a 70mm to 100m ED or APO scope of some sort.  The difference in performance as compared to a similar f-ratio achromat is astounding.  My FPL-51 doublet AT72ED started me down this road around 2013.  In 2019, I upped my game and got a TS-Optics 90mm FPL-53 triplet APO after realizing what features mattered most to me.  Both are a lot of fun to use and hold their own against larger reflectors or compound scopes.  The best part?  No filtering is needed for clean, sharp images.

It seems a rather simple effort of trial and error under the stars/planets to find the cutoffs for various achromat f-ratios at both spectrum ends to make them more usable by eliminating most of the unfocused light ruining sharpness.  Once these are cutoffs have been established, either dyed or interference filters could be made to pass only the well focused central region tailored to each focal ratio.  Sure, the color balance would be way off being a teal blue-green mixed with yellow-orange, but they could be sold as general purpose planetary and double star splitting filters for achieving the best sharpness while retaining as much of the spectrum as possible in fast achromats.

3 hours ago, Franklin said:

Have you tried the Wratten #11 yellow/green?

No, the color makes me queasy.  I suppose I'll give one a try sometime.  I also intend to get a GSO or Meade (Japan) Yellow #8 just to see how it compares to the Yellow #12A.

The #11 Yellow-Green is a bit aggressive in the blue, but does let in some yellow and orange while squashing most red:

I've acquired a Hirsch #12A and a spectrograph in the last year and have done some testing of various yellow filters with the spectrograph, an artificial star (not a great one by any means, just a foil pinhole over a Cree LED tactical flashlight), and with my ST80.  First the composite image of several yellow filters in increasing violet/blue cutoff order.  The named ones with R## at the beginning are Roscolux filters that did a good job of sharply cutting-off violet/blue at a particular wavelength.

I didn't bother with the artificial star image of the Minus Violet filter because it wasn't handy when I was doing that particular test.  However, it should show plenty of violet.

• From the above, the Yellow #12A would appear to be a good contender along with the R312 Canary, so I tried them all out in my ST80.
• In my ST80, everything from Cheap Yellow down to Yellow #12 filtered out practically all visual violet when viewing Jupiter.  I'll have to try repeating the test on Venus sometime to be more equivalent to the artificial star.
• The minus violet did practically nothing to filter visible violet fringing.  It also added no noticeable yellow cast.
• The cheap yellow filter left a slight yellow cast to the image as predicted by the artificial star while leaving a bit of violet.  I think poor filter material led to scattering.
• The Hirsch #12A and R11 Light Straw actually looked the best.  Neither one imparted much of any yellow tone while at the same time squashing nearly all visible violet.  I was surprised at not seeing violet fringing in the latter despite the artificial star predicting it would be there.
• The R312 Canary imparted a noticeable yellow cast, as did R310 Daffodil.  Both did a good job of eliminating violet despite the artificial star's prediction of a bit of violet for the latter.
• The GSO Yellow #12 once again imparts a very strong yellow cast while completely squashing all violet and most of the blue.  At that point, I could clearly see red fringing, so it was back to light green filters to squash all fringing.
• Red fringing intruded in all views once violet was diminished or eliminated, so a true anti-fringing filter would need both violet and far red cut-offs.  A wide teal-yellow-green filter from deep blue to red-orange would probably work for this purpose.  I just don't know of any, even from Roscolux.
• It's too bad the Hirsch Yellow #12A is so hard to find used as it does a really good, and yet subtle, job of cutting out violet while leaving most blue.  The R11 Light Straw would seem a viable, and available, alternative once cut and fit into a filter holder.  A large sheet of it is cheap enough that it might be worth covering the entire objective to see how well that works.

10 hours ago, Carbon Brush said:

10th March or 3rd October?
When will the US join the rest of the world?

In conversation, does the rest of the world always say 10th of March or 10th March?  Folks in the US are just used to saying March 10th, and so we write it the same way.  The 4th of July and Cinco de Mayo (5th of May) are the main two exceptions that I know of.

Did you use mahogany wood?  It looks beautiful.

Try opening both eyes at the same time and merging the red dot in the dark window with the sky view seen by the unobstructed eye not looking through the window.  I apologize in advance if you are blind in one eye.

Try a Yellow #8 to lightly filter out the purple haze.  It can sharpen up the views a bit.  I've found the appearance of lunar mare become more contrasty in my ST80 with a light yellow filter.

Try a Green #56 to improve the snappiness of the focus by filtering out both ends of the spectrum that focus at different distances from green, which is what the achromat is optimized for.  Even with premium eyepieces and dielectric diagonal, the only way I could make out the phase of Venus in my ST80 was with a light green filter.

It could be that there's nothing that can be done to improve the view with the included diagonal and eyepieces, but it might be worth a shot.

14 minutes ago, Ratlet said:

The redlines have a reputation for kidney beaning but is it the case that it's the eye not being at the right place due to eyerelief?

The 6mm and 9mm versions certainly do suffer from SAEP.  Both also perform fairly well in faster scopes.  The reason for both results is the 6 and 9 employ a Smyth lens group to amplify the focal length.  This slows down the light cone, improving edge performance.  However, the matching of the Smyth and image forming groups was poorly done, leading to SAEP.

The 15mm and 20mm versions have no Smyth group.  They are purely positive designs which rarely suffer from SAEP.

18 minutes ago, Ratlet said:

It's also why I don't even consider using my 32mm barlowed, it's too hard to keep my eye in right place.

Barlows tend to push out the eye relief and induce SAEP in my experience.  Both make holding the exit pupil more difficult.  This may be what you're experiencing with the Barlowed 32mm.  If you used a telemagnifier like a TV PowerMate instead, you would not experience either issue.

3 hours ago, bosun21 said:

I wouldn’t if I was you unless you’re a lover of kidney beans.

No SAEP in the SVBONY Redline 20mm, if that's what you're alluding  to.  Notice there's no significant shadowing in it's AFOV image in the third row, far right.

3 hours ago, Ratlet said:

Tempted to order a SVBONY Redline 20mm.  Not expecting miracles out of it, but I think it would be nice to compare a similar slice of the sky with different eyepiece FOV and exit pupils.

It is a poor performer in the outer field below f/8 for certain.  However, at f/18 in my binoviewer, they are terrific as a binoviewing pair for eyeglass wearers.

Here's my write-up on it:

I've found that the longer the eye relief, the easier it is to see the entire field all at once in a relaxed manner, with or without eyeglasses.  My 17mm ES-92 with 16mm of eye usable relief has a much easier to take in AFOV than my 20mm Meade 5000 UWA with its 12mm of eye usable relief even if I take off my eyeglasses.  Part of that may be my deep set eyes.

To examine the edges, the required head tipping seems more extreme in the Meade despite having a narrower AFOV.  The problem is, adding long eye relief to SWA, UWA, and HWA eyepieces generally makes them bigger, heavier, and more expensive than their limited eye relief equivalents.