Louis D

Those star tails look like line scanner artifacts.

4 hours ago, Astronomist said:

Thanks everyone , that's kind of as i expected with the diffraction effects. Out of interest @Louis D, how effective is your apodising mask for high magnification? Does it really help with poor seeing very much?

I've only tried it during good seeing.  It seems like it might increase the contrast of low contrast details on Jupiter and Mars, but using a binoviewer is far more effective.  During the last Mars opposition, I tried it with binoviewing, and it seemed to increase contrast a tiny bit more.  However, the psychedelic effects are pretty hard to ignore immediately surrounding the object.  Overall, I wouldn't recommend taking the time and effort to make one.  It's not particularly hard or expensive to make, but it seems like a waste of time and storage space.

Here's the mask itself made from two sheets of crafting foam board, three offset layers of black window screen spray painted flat black, and some short screws (not visible) around the perimeter holding the layers together and in place:

The taped nubs are the heads of two long bolts threaded through the board that the mask hangs off of while on the front end of the telescope tube.

On 19/04/2023 at 08:18, mikeDnight said:

You'll have to ask the awesome Janice Broughton about that. I was in love with Janice from being 8 years old, but when I reached my mid teens, for some inexplicable reason I became a Neanderthal.  She was blonde with bright blue eyes and a wonderful sense of humour.  Then one day as I was walking along the road leading to the local park I heard her sweet voice say " Hiya Michael"!  I replied with a grunt and walked on without saying much. What an idiot! My heart still burns when I think about her.  She's now a nurse living in Australia, so if nothing else her medical training under my guidance paid off. 💔

“Tis better to have loved and lost
Than never to have loved at all.”

― Alfred Lord Tennyson

Try it with some yellow (#8 or #12), yellow-green (#11), or light green (#56) filters to see if narrowing the pass band sharpens things up a bit on high contrast objects like Venus and the moon.

Here is @Geoff Lister's 127 Mak backpack setup:

I setup my daughter with a similar rig for her camping trips.  I don't know about Sweden's secondary market for telescopes, but 127 Maks come up for sale at around $300 here in the States all the time.  When I bought hers in 2018, they were going for $200 apiece.  Inflation has crept into the secondary market, apparently.

I have a 127 Mak myself.  You can use it at lower powers just fine while you wait for it to acclimate.  It never needs collimation.  I love that there is no focuser flex.  I also love the short lever arm on a manual alt-az mount.

@Jiggy 67 What's the advantage of the EQ6-R-Pro over the ZWO AM5 for visual observing?  For about the same money, the latter is far lighter, and can be used without a counterweight for lighter loads, something I don't think the EQ6-R-Pro is capable of doing.  I'm thinking about getting an AM5 with a ZWO TC40 carbon fiber tripod to use visually in alt-az mode instead of using a similar capacity manual alt-az mount like an AZ-100 similarly equipped with encoders.

Might look similar to my apodizing mask:

@Peter Drew are you sure about that?  Isn't the secondary cutting an elliptical conic-section from the light cone, and aren't all ellipses symmetrical across both axes?

I assume secondaries are diagonally cut from cylinders and are also ellipses.  Shouldn't it be possible to get the major and minor axes to match that needed to match that of the cone's ellipse?

On 12/06/2023 at 06:58, DaveS said:

If they're talking about what we laughably call the UK Space Industry then they need to get in touch with Jordan Wright, the Angry Astronaut. isn't it ironic the the best informed person is an Anglophile American?

On 12/06/2023 at 15:03, DaveS said:

We put a satellite into orbit in 1971 despite government interference, then promptly went to sleep. I blame a mentality in the civil service that knowing Ovid is more important than understanding Schrödinger.

On 12/06/2023 at 16:11, DaveS said:

The negativity that you might perceive is born of my frustration at our lack of progress in launching, when I see any number of US private companies (Not just SpaceX) launching satellites.

Texas alone has SpaceX, Blue Origin, and Firefly Aerospace off the top of my head.  Then there's NASA's Mission Control in Houston.  As far as aerospace, Lockheed Martin, Boeing, Raytheon, Sikorsky, BAE Systems, L3Harris, and many others have operations here as well.  And that is just one state in the US.

22 hours ago, pipnina said:

Your selection of films is limited however, and may shrink further as Fujifilm seems to be having various troubles getting raw material for their existing formulas, and some of their best stock (velvia 100) is actually banned in the USA for containing certain chemicals their agencies aren't happy with.

I'm picturing US customs confiscating it from Japanese tourists upon arrival at US ports of entry.  If they get them developed back in Japan, there shouldn't be much, if any contamination issues in the US.

The EU bans plenty of stuff the US considers safe enough like titanium dioxide which can be used to make candy coatings more vibrantly colored.

On 13/06/2023 at 09:15, wookie1965 said:

I already have a Herschel wedge I would like to see proms 

See this recent thread you started:

If there are no electronics, I would mainly worry about plastic, rubber, and glued parts.  All will become brittle and crack/crumble more quickly when exposed to high heat in my experience.

If there are any press-board components, the glue holding them together might be compromised at some point by heat.  I know I have trouble with press-board absorbing moisture and swelling in non-climate controlled storage areas.

I would think metal and glass parts would be completely unaffected by temperature.  Sure, they'd take longer to reach thermal equilibrium when you take them out to observe, but they wouldn't be damaged or degraded like plastic, rubber, and glue.  However, high humidity could quickly lead to fungal growth on them.  I keep my equipment stored in my climate controlled house to avoid these issues with our Gulf humidity.  My Dobs' mirrors look terrific for being 25+ years old.

I have no idea if your 10" Dob has any non-metal, non-glass parts or uses any glue.

As far as binocular astronomy, I have alternated between my 8x42 and 15x70 binoculars for decades now.  The former works well for wider angle views of chunks of constellations while the latter works best on cluster rich regions or large star clusters.

I recall hypering Tech Pan film used to be quite popular back in the days of film.  Tech Pan hasn't been made since 2006, though.  I doubt you could find hypering equipment today, either.

1 hour ago, pipnina said:

Cameras now have micro lenses, and now that you mention it I recall a special kind of camera that uses a similar trick to bypass the need for perfect focus by having the lens bring different sub-pixels underneath it to a different focal plane, allowing for software controlled focus in post-production.

Yes, Lytro's plenoptic cameras never found a market niche.  They were mostly useful for macro photography.

However, computer controlled focusing of camera lenses allows for rapid fire captures of multiple images at different focus points.  These can then be combined in post using dedicated image processing software (just like astrophotography has its own dedicated post SW) into an image with much larger depth of focus.  This seems to be the direction macro photography has headed over the past decade or more.

17 minutes ago, rwg said:

I've been waiting for someone to build a sensor that does this *at the pixel level*. Just like we have microlenses and (for colour cameras) filters on each pixel now, imagine a camera where each pixel had a prism arrangement splitting the photons between 3 separate detection sites.... Once camera, one shot colour, no 66% loss of photons.

It might seem far-fetched, but the sort of features built into camera pixels now were pretty far fetched only 15 or 20 years back.

Rather than a prism arrangement, the Foveon sensor (introduced 20+ years ago) had stacked photodiodes of differing spectral sensitivities at the wafer level.  As you can imagine, the red channel being at the bottom of the stack had the lowest sensitivity and highest noise of the three, which is unfortunate for Ha imaging.  However, it does get rid of the Bayer anti-aliasing filter which reduces resolution.  On the flip side, the article mentions color noise at low light levels, which is exactly what DSO imaging is.

Perhaps it might be more promising for solar system imaging where the light levels are generally quite high, and enabling one-shot color without an anti-aliasing filter might be advantageous.

Someone on CN seems to have done the measurements.

3 hours ago, Chefgage said:

Thanks. Having re-read what I posted I was indeed confused (I am going with the amount of vodka drank:) )

Been there, except with tequila. 

Just did a google search on tablet holder with clamp and came up with plenty of options to hold a table on the end of an arm which has a clamp at the other end to attach to a tube or similar.

I've seen plenty of videographers' run and gun rigs with tablets attached in various ways to the superstructure so they don't have to keep their eye mashed into a viewfinder peephole, so I know there are good solutions out there to be had.

On 09/06/2023 at 14:04, Chefgage said:

I am currently away in Cyprus, mars is at an altitude of 16' at UTC 19:00. So the same time.

Yes, but not the same local time.  That was my point about being a slave to UTC when comparing the local views at the same time.  Taken to the extreme, you might be asking why is it so bright out when it's UTC 00:00 (midnight Greenwich) in New Zealand.  It's the same time, so the sky should be the same, right?

BTW, does anyone know why the current popularity of unboxing videos exists?  I find them completely uninteresting.  At the end of the video, I still have no idea if the item is any good for its intended use.  I only include images of the packaging in my reviews to satisfy those who find that sort of thing essential to a review.

On 01/05/2023 at 04:12, Drkneb said:

Another oddity was that my observing partner didn't need to adjust the focus which we've had to do essentially any other eyepiece we've ever used together for the past 12 years.

Do both of you always swap views after focusing for infinity using distance vision eyeglasses or contacts?  If not, it is unreasonable to expect the eyepiece/telescope combination to be focused at the same distance for two observers that have native eye focus at different distances.  If you are focusing for infinity with other eyepieces and both observers have distance corrected vision, I'm not sure why you needed to adjust focus with those other eyepieces and not the ES-92 17mm.

20 hours ago, Chefgage said:

Current situation. At home in the UK where I live at UTC 19:00 mars is at an altitude of 40'.

I am currently away in Cyprus, mars is at an altitude of 16' at UTC 19:00. So the same time.

I thought the further south you went the planet's would be higher in the sky?  Am I wrong or is the the vodka that has made my brain not work

Why would you use UTC instead of local time?  If you had used 19:00 local time (assuming both consistently use Standard or DST/Summer Time), then Mars would have indeed been much higher in Cyprus.

I only use prism diagonals for correct image viewing.  For everything else, I use GSO dielectric mirror diagonals.  I've never felt the need to upgrade from them.

On this topic, I have a vague recollection that some folks have noticed that prism diagonals correct chromatic aberrations in certain scopes, but I can't recall the details.  Does anyone else recollect this or is my mind on <insert illegal drug name>?

As others have said, I use nebula filters for some nebula observing.  I've tried various filters on Jupiter and Mars with marginal success.  Of course I use a solar filter or wedge with the sun.  I tried some vintage color line filters for solar, but didn't notice much improvement.

All of the above work with any scope.  However, for my fast achromats, I have been extensively trying out various combinations of yellow/long-pass/minus-violet and cyan/short-pass/blue-green filters on Venus and the moon to block unfocused violet-blue and red light to vastly sharpen the image at higher powers.  You end up with a pale lime-green color cast.  I've also tried various light green filters which achieve similar results over a narrower passband and lower transmission.