Louis D

On 13/02/2022 at 11:53, OK Apricot said:

My mind has been wandering today, thinking how I've got my light bucket, now I need something laser sharp for the solar system.

Have the primary refigured to 1/10th wave or better if it isn't already, decrease the size of the secondary to no more than 20% obstruction by diameter, and replace the focuser with a low profile focuser.  My best planetary views have been through 8" to 12", well collimated Dobs with custom mirrors like Zambuto and an undersized secondary.  The low profile focuser gets the eyepiece closer to the secondary to grab as much of the reduced cone of light as possible.  Of course, it might be cheaper to just start over and look for a used custom made Dob with full goto.

16 minutes ago, cloudsweeper said:

What would this be as an add-on for the basic 8SE?  I'd really like something to improve its sharpness without spending a fortune on an Edge HD model.  

Aperture (8" or more),  GoTo, and sharpness would be a great combination!

Doug.

I'd probably start with a Celestron 0.63x reducer/corrector if you already have the 8SE.  I can't find an SCT corrector that isn't also a focal reducer.  However, these don't play well with short focal length eyepieces.  From what I've read over the years, you don't want the R/C present at high powers.  I see something similar with the GSO CC in my Dob and the TSFLAT2 in my fracs.  Both contribute spherical aberrations at high powers that overshadow any intended correction.

The Starizona R/C is much more expensive, but probably achieves better correction.  I'm not sure how applicable it would be to visual work, though.

The difficulty of trying to get absolute sharpness with SCTs is probably why other designs are more popular for high power visual work.

1 minute ago, cloudsweeper said:

Thanks, @Louis D - the paper and chart indicate that an Edge HD would indeed be better for visual than the basic SCT, and that is what I want in order to get tighter splits more clearly.

When you say:          "My point is, even on axis, SCTs need some optical corrector help at the rear baffle tube/port."        - do you mean a corrector for the basic SCT would improve the sharpness, or that such a corrector is built in to the Edge series?

Doug.

 

Both

16 minutes ago, cloudsweeper said:

I've always thought my 8SE SCT was less sharp ("softer") than the Dob (and fracs of course).  It is well collimated, I believe.  I had contemplated eventually going for an Edge HD, but don't they have essentially the same optics as the basic SCT, except for a field flattener for AP purposes?  If so, I guess there would be no advantage for a visual-only person like me.

I look forward to comments on this!

Doug.

 

Read this Celestron whitepaper on the EdgeHD.  Even in the center, the spot sizes are tighter than a typical SCT:

It might also be possible to get similar results with a Starizona flattener/corrector:

My point is, even on axis, SCTs need some optical corrector help at the rear baffle tube/port.

1 hour ago, rwilkey said:

No filters will help you with galaxies and globular clusters, I am afraid, you just need clear skies.  

If you've got enough aperture to resolve a GC at high enough power, light pollution isn't such a big issue.  For instance, M22 is barely visible as a brighter fuzz patch near the Teapot asterism from my backyard at lower powers, but at over 200x in my 8" Dob, it breaks up nicely into teeny tiny pinpoints of light for the most part.  Not all GCs will resolve with only 8" of aperture, though.  In fact, only a few of the closest/largest ones resolve nicely for me.  I need to get a bit further south and seek out a clear view of the southern horizon sometime to see if I can bag Omega Centauri.  It should be just doable from southern Texas IIRC.

48 minutes ago, Starslayer said:

Picture?  🤣  

I have actually decided that I do not need the 9 x 50 on the ST102 but I have upgraded the RDF to a Baader Skysurfer 111 and it is very good.  The 9x50 is now on my 6"sct with the addition of a Baader universal shoe and again works well although I have the Telrad on there too.  I think a rdf of some sort is essential ( for me at least ) as the start point. 

I'll try to remember to snap a pic the next time I have one of them set up.

On 14/02/2022 at 04:06, ScouseSpaceCadet said:

Since then several others have started selling similar aluminium cast brackets . I can't vouch for the seller, that link is just an example.

I have a couple of these triple mounts for different scopes.  They are quite robust and work very well.  You have to be careful about where you put the various finders in the three shoes or you won't be able to get your eye in the proper position or get them all to fit next to each other.  I put my RACI finder (the heaviest of the finders) as far over as possible to keep it more in line with the altitude axis so I get less backward tipping at high altitudes.  Next goes my QuikFinder on an adapter from ScopeStuff in the middle position.  Last goes my GLP sight because it ends up almost straight ahead of the eyepiece in the diagonal, which doesn't matter for it but would make using the QF in that position next to impossible without tipping the eyepiece out of the way.

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

A C8 is very grab and go especially if stored in a cool garage so you don't have cool-down time. It outstrips the performance of my excellent little APM 80mm triplet on planets.

Why is it that SCT planetary images look good, but every time I look at planets visually through SCTs at star parties, the views are always upstaged by nearby Newts with custom mirrors of similar aperture?  The only time an SCT gave comparable visual planetary views for me was through an 8" EdgeHD.  It was just as sharp as the views through the Dobs with custom mirrors.

🤔 And here I thought the Powermates weren't supposed to alter focus position of an eyepiece by much, if any.

Try pulling the eyepiece upward out of the PM to see if that helps at all as well as pulling the PM up out of the focuser.  Seems weird that focus position is so far off as with a long Barlow.  At least with the latter, it has a 2" to 3" insertion tube, so you just insert it partway and lock it down once focus is reached.

On 12/02/2022 at 17:15, Peter Drew said:

As a 2 quid a week engineering apprentice in 1958 I couldn't even afford a used telescope let alone a new one.  Ended up having to make my own, still look where that got me!      🙂

As a college engineering intern for General Motors in 1986, I was paid $8/hour.  Considering the US Federal minimum wage was $3.35/hour back then, it wasn't that much when you consider I had to pay for a room to live in near Detroit and buy my own food and pay for transportation out of that money.  Since I was paying my way through college, it wasn't like I could just ask my parents for financial help.

The US Federal minimum wage was $1/hour back in 1958, so you were really underpaid, and UK labor laws were pretty lax over there back then.

On 12/02/2022 at 14:31, ScouseSpaceCadet said:

Playing golf, much like tennis, is still very much the preserve of those with above average disposable income

Off topic a bit, but don't y'all have outdoor public tennis courts that are free to play on?  We have them at many city and county parks, middle and high school grounds, and even a few churches with large grounds have them.  Then, all you need is a racquet and some tennis balls.  With so many, it's not too difficult to know which are generally available and when.  They are almost as common as outdoor half court basketball courts around here.

If you had said squash, handball, or racquetball, I'd have agreed.  Those courts are more difficult to find, generally being indoors.  You have to have a rec center or other club membership to use them.

1 hour ago, banjaxed said:

Seems strange to me that any country (countries) deliberately make it difficult to buy from them 🤔

No, but plenty of countries deliberately make it difficult to sell into them.  Tariffs, duties, taxes, inspections, quarantines, proof of origin, etc.

For instance, lots of countries now insist on the seller collecting all taxes and tariffs due before shipping and remitting them to whatever country it was sold into instead of leaving it up to the buyer to pay them locally before receiving said items.  That's a whole lot of extra paperwork to deal with as a retailer.

And no optometrist ever caught this during an eye exam?  You have to look through a binoviewer-like device (a phoropter) that should have flagged this.

I believe prism correction in eyeglasses would solve your problem based on your description.

I found that the only alignment problem I was having with my Arcturus BVs, which do have self centering holders, was due to eyepieces with undercuts tipping in the holder during the tightening process.  I have to cram them down while tightening to prevent them from popping up at an angle.  I should just fill the undercuts with pinstriping tape.

20 hours ago, Zermelo said:

Some time ago I saw a message on their site saying that they weren't shipping to the UK after Brexit because of the hassle with taxes and duties.

I haven't looked there since, so I don't know if they changed that.

Same reason most Americans won't mail items outside the US.  Too much hassle and higher risk on transactions.

I think I recall @Don Pensack of Eyepieces Etc. mentioned that he won't be doing business with Europe anymore due to various new regulations that are onerous to deal with.

13 minutes ago, ninjageezer said:

i have read in an F4.7 anything wider than about 60 degrees would only give to much softer edges

Then invest in a coma corrector.  The most expensive option is the Tele Vue Paracorr T2 and the cheapest is the GSO/Revelation CC.  The ES HR Variable CC falls in between, but requires the most in-focus of the three.

You also have to consider how far your nose bridge protrudes relative to your eye sockets and how wide it is.  Someone with a very flat face would be much less restricted in eyepiece choice than someone with deeply set eyes and a prominent nose bridge, like myself.

The better question to ask is "Is amateur astronomy being lost to ever increasing light pollution?"  For example, in recent years, outdoor LED lighting has made matters worse by spreading stray light across the visible spectrum making light pollution filtration all but impossible.

So, 1.6mm off on the low side for the converted Tele Vue specified value of 40.6mm for the 13mm NT6.  The TV spec'ed 43.2mm value for the 19mm Pan and 16mm NT5 is off by 1.1mm on the low side for the former and 1mm off on the high side for the latter.  Even if TV had some rounding going on, I would have expected the 13mm NT6 and 16mm NT5 to have the same listed width.  My faith in Tele Vue spec accuracy has been shattered. 😱

Here are a couple of references describing color filter use cases.

I have the Zhumell OIII which cost me $10 from Hayneedle back in 2014.  This 2009 review on CN shows why it's barely usable.  Its passband is shifted 10nm to the right of where it should be.  I can verify it makes little difference other than dimming nebula along with the background.  Contrast barely increases compared to a 1990s Lumicon OIII I own.

The review does praise the Zhumell UHC which I wish I had picked up for cheap back then instead of the OIII.  It seems to hit the mark where the OIII missed.

5 hours ago, DrMike said:

I have a decent set of both 2” and 1.25l” eyepieces, but can anyone recommend a decent set of coloured filters for moon/planetary visual observation? The basic 4 colours, a moon and possibly polarising filters.

I’ve seen several sets on sale, ranging from dirt cheap to ridiculous.

If you really want to try some color filters for cheap, order this set from China.  They're a bit cheaper here.  I recently received mine and they seem decent enough, although I've yet to try them out under the stars to verify if they are optically flat and don't introduce reflections.  They arrive individually plastic sleeve wrapped inside the displayed box, which is inside another clear plastic sleeve.  Mine came padded with thin closed cell foam around the entire case that I cut to size to pad the bottom/sides of the case and the underside of the lid to keep the filters from rattling about.  They don't have front side threads, so you can't stack any other filters onto them.  They are also a bit constricted on clear aperture, so not a good choice for widest true field 1.25" eyepieces.  The filter cells are a nice hefty metal, though.

I bought them mostly for the magenta filter which is very hard to find elsewhere.  I verified that it does a good job of passing red and blue while suppressing green by taking an image of a sunlit translucent surface through it and checking the RGB channels for intensities.  I plan to try it on Mars at the next opposition.

The green is also a nice light shade that blocks basically all red light according to my tests.  It does let some blue through, so it's not chromatically pure green.  I paired it with a #12 Yellow filter with front threads to block that blue light and verified it can produce a nearly pure green color in that configuration.

The red is fairly light as well, and yet has no orange cast at all to it.  I'll have to try it on Mars.

The yellow is a bit pale like a #8 Yellow, but might help cut stray violet light on a fast achromatic refractor.  Since I already had a #12 Yellow filter, it worked out fine to get this one.

The orange is a bit too dark for my tastes.  It works, but I'm not sure what objects it would be useful for.

The blue is a bit too dark as well for me.  It's probably fine, but I prefer a light blue filter for Jupiter.  Less is more in that use case.

Edit: I just noticed you're in the US.  Unfortunately, the seller I bought from is sold out of this set.  Another seller has it here for a bit more than I paid.  I noticed these sets and these sets with slightly different colors are now available at a slightly higher price, and I don't know if the colors are in the same hues and shades as my set, but they appear to have more clear aperture and might have front threads.  The case sure looks slick.

The 16mm NT5 is listed as the same diameter as the 19mm Pan, 1.7 inches.  That's 2.5mm wider than the 13mm NT6.

I don't know about your side of the pond, but Agena Astro sells several sizes which are well thought of on CN over on this side of the pond.

The wider the field, the harder it is to take it all in at once using binoviewers because you can't look off axis without losing one or both eyepiece views.  You are forced to rely on peripheral vision more and more the wider you go.  I find 60 to 70 degrees to be plenty wide when binoviewing for these reasons.  That, and apparent fields of view appear at least 5 degrees wider in binoviewer usage for some psychological reason.

I've recently found that the SVBONY 68° Ultra Wide Angle 20mm work great in binoviewer usage as I detailed in this post.  Of course, if you're not using a Barlow lens element to reach focus in a fast scope, they're not going to look as good to the edge.  However, since I'm operating at 3x with my Barlow nosepiece (a Meade 140 2x), these eyepieces are fantastic for an astigmatic eyeglass wearer like myself.

For very high powers, I use a pair of Celestron Regal 8-24mm spotting scope zoom eyepieces with the 3x nosepiece.  They were also sold under the Olivon label with their spotting scopes.  It's just too much of a pain swapping two eyepieces to change high powers in a binoviewer, so I compromise with zoom eyepieces.  However, at the slow f-ratio when operating at 3x, the zooms look fantastic as well.