A box of (lesser) green and black - or what you can achieve with SGL classifeds

[Louis D]

11 hours ago, jetstream said:

Clark

"Optimum Magnified Visual Angle

A low-contrast object is more easily detected if it is larger. For an extended object such as a galaxy viewed in a telescope, magnification does not change the contrast with the background, because both the sky's and the object's surface brightnesses are affected equally"

Um, not necessarily so.  If it is so large that its energy is too spread out to detect, you're just not going to see it.  Try detecting the North American nebula in a very large Dob at high power.  If you swing the Dob rapidly enough across it, you might just detect the brightness change as you sweep past the edges, but that's about it.  It's generally easier to detect or even "see" it with wider field instruments at lower powers.

[jetstream]

29 minutes ago, Louis D said:

Um, not necessarily so.  If it is so large that its energy is too spread out to detect, you're just not going to see it.  Try detecting the North American nebula in a very large Dob at high power.  If you swing the Dob rapidly enough across it, you might just detect the brightness change as you sweep past the edges, but that's about it.  It's generally easier to detect or even "see" it with wider field instruments at lower powers.

The object you describe is large already, meaning extra mag is not needed and is best viewed with a 5mm-6mm exit pupil, regardless of mag. The issue you describe can be attributed to "seeing" through the nebula, a common issue in large telescopes. I observe this easily in my 15" and 24" dob, but again the narrow TFOV means seeing through the object happens.

29 minutes ago, Louis D said:

A low-contrast object is more easily detected if it is larger.

This says it all- NGC 7000 is "large" already. Somewhere I have a formula for object size in arc min at different mags in the eyepiece but I don't use it, all this is easy if a few things are accepted.

The true advantage to large scopes (fast btw) is the fact that they give "image scale" (size in EP) at a good eye illumination (exit pupil). An example of this is the Jelly fish nebula IC 443- easy direct vision in my 24" because the focal length gives great image scale and at an eye illumination that works well with filters -4.5mm-6mm.

Same goes for the "Little Veil" SH2-91.

So yeah, all this does work and illustrates the importance of exit pupil and object size.

Edited April 1, 2020 by jetstream

[Louis D]

9 hours ago, jetstream said:

So yeah, all this does work and illustrates the importance of exit pupil and object size.

And illustrates no one telescope is the right tool for every job.

[JOC]

16 hours ago, scarp15 said:

"The Globular's are coming soon; to a back garden near you"

Thank you - I shall certainly be bookmarking this thread to come back to for advice and summer targets.  I am absolutely chuffed to bits that none of you minded my excitement at my full set of EP's and have written such nice things - it's been a really lovely thing in the middle of this lock down crisis and you have all made me very happy - thank you 😄  

[JOC]

Lots of you have mentioned my other Baader - the 31mm aspheric modular.  Now there is still space in my 'top end' case as you can see - you know that it currently tops out at 17.5mm.  Currently the 31mm is in my 'take it to outreach activities case'.  I just wonder how it lines up with it's competition?  Shall I hold out for a better grade of low magnification EP at some point, or is it 'worthy enough' to add to the 'top end' box?

[Louis D]

15 minutes ago, JOC said:

Lots of you have mentioned my other Baader - the 31mm aspheric modular.  Now there is still space in my 'top end' case as you can see - you know that it currently tops out at 17.5mm.  Currently the 31mm is in my 'take it to outreach activities case'.  I just wonder how it lines up with it's competition?  Shall I hold out for a better grade of low magnification EP at some point, or is it 'worthy enough' to add to the 'top end' box?

It all depends on how long you spend using it before moving up in power.  Certainly the 30mm APM UFF is better corrected, but if you just use it to locate and center objects rather than observe them, then that advantage is largely lost.  I used a 38mm Rini MPL for years as my widest field and its outer field astigmatism never bothered me.  Then I compared it to my 27mm Panoptic and realized how much performance improvement would be had if I upgraded.  I tried Rini's 42mm Erfle, but it was poor as well.  I got lucky that the Meade 5000 SWAs went on fire sale in 2013 and picked up the 40mm version.  Wow, what a difference!  Now, when I go back to the 38mm Rini (which I keep for sentimental reasons), I can't believe I could have ever accepted its poor performance for so many years.  Here's images showing the differences in the sharpness.  Having never looked through a 31mm Baader Aspheric, I'm not really sure where it lines up with these performance wise.  I'm guessing the 35mm Aero ED might be similar based on size and price.  Good, but not great.

[JOC]

7 minutes ago, Louis D said:

Here's images showing the differences in the sharpness.

What an interesting photo - you can certainly see the lack of edge to edge sharpness in some of them.  About the only thing with the same degree of edge to edge sharpness as the M5000 SWA 40mm is the 32mm Sirius plossl and obviously that has a smaller FOV anyway.  How do you get a photo like that please?

[Louis D]

2 minutes ago, JOC said:

What an interesting photo - you can certainly see the lack of edge to edge sharpness in some of them.  About the only thing with the same degree of edge to edge sharpness as the M5000 SWA 40mm is the 32mm Sirius plossl and obviously that has a smaller FOV anyway.  How do you get a photo like that please?

I put the target in the kitchen hanging from a cupboard (wedged under its door).  I then went way out the edge of the front room, about 35 feet away, and setup my AT72ED refractor.  Luckily, I have an open floor plan home.  For each eyepiece, I put the edge of the rulers at the field stop and on the horizontal center line.  I then focused each eyepiece on the target and then carefully used my Samsung Galaxy S7's camera to take images of each eyepiece's field of view.  The tricky part is centering and leveling the camera and keeping it at exactly the exit pupil distance so the field stop is sharp, but blackouts haven't begun showing up.  Here's the result for my 23mm to 30mm eyepieces.  The edge images were taken by tipping the camera to point directly at the edge since the diagonal of the camera can only take in about 70 degrees.  The "full view" images were taken with an LG smartphone's super wide angle lens that is, unfortunately, lower resolution. I then scaled the image so the central parts match in magnification with the Samsung images.

[Don Pensack]

On 28/03/2020 at 08:33, JOC said:

So probably as many folks have done I've coverted a full set of eye-pieces.  I've seen those beautiful and extortionantly priced boxes of green and black that many own and wished for similar, but I could never justify that amount of expense for what little observing I actually get to do.  However, from the eclectic assortment of cheaper EP's that I accumulated from SGL classifieds I realised I much preferred an EP with plenty of eye relief and a wider field of view.  I then got a chance on the SGL classifeds board to buy a Baader Morpheus 14mm at a good price.  What a difference - this really seemed to be a great thing and on the moon it was terrific.  I wanted more - the trouble was they were mostly upwards of £190 a pop sometimes clearing the £200 mark depending on the seller - I couldn't afford them.  Then a second one popped up on SGL classifieds (I forget which now) - sod it, it was around the same price as the first one - ouch went the bank balance, and again and again and again!  Of course the more I got the more I wanted to complete the collection and thanks to SGL classifeds I am finally there - it took a while, but I now own the whole collection for a fraction of what I could have got them for new.  Bro had a really nice old metal flight case, so I've sprung for pluckable foam and here is my 'best' collection of EP's - it rather ruins the look to add the Pentax XW 5mm, but I know that's also rather nice glass so it does belong there I think.  The only thing is the Morpheus stops at 17.5mm and that rather misses on the wider field views of the sky, but for the sake of my bank balance that's probably a good thing and I have some lesser EP's that do serve in that capacity.  

I do think I am very lucky - it isn't a box of classic green and black, but I'm rather chuffed with it.

Try a 30mm APM UltraFlat field eyepiece to round out the set.

Then your training will be complete.

[JOC]

All the Morpheii have the ability to seat into a 2" focusser.  Novice question, is this just for convenience or is there any advantage to seating them into a 2" focusser - I guess they are possibly more stable, but I can't see how it can affect the view if the final barrel is only 1.25"

[jetstream]

4 minutes ago, JOC said:

All the Morpheii have the ability to seat into a 2" focusser.  Novice question, is this just for convenience or is there any advantage to seating them into a 2" focusser - I guess they are possibly more stable, but I can't see how it can affect the view if the final barrel is only 1.25"

Some scopes can benefit from this focus point wise, and the option is great to have IMHO.

Off topic JOC- have you seen the Swan nebula?

[JOC]

18 minutes ago, jetstream said:

Off topic JOC- have you seen the Swan nebula?

I haven't, but I am sure I saw Cygnus out the other night - the big W - yes?  If so it's not beyond the realms of possibility that knowing that I could find it.

[John]

27 minutes ago, JOC said:

All the Morpheii have the ability to seat into a 2" focusser.  Novice question, is this just for convenience or is there any advantage to seating them into a 2" focusser - I guess they are possibly more stable, but I can't see how it can affect the view if the final barrel is only 1.25"

They are 1.25 inch eyepieces despite the 2 inch section of barrel. You need quite a bit of outwards focuser travel to use them with the 2 inch section inserted.

BTW - the "W" is Cassiopeia. Cygnus is a Summer constellation and looks like this:

[JOC]

1 minute ago, John said:

BTW - the "W" is Cassiopeia. Cygnus is a Summer constellation and looks like this:

Thanks John, Mmmm...big cross in the sky I don't know if I've spotted that previously or not.

[jetstream]

5 minutes ago, JOC said:

I haven't, but I am sure I saw Cygnus out the other night - the big W - yes?  If so it's not beyond the realms of possibility that knowing that I could find it.

Johns right and its great to hear youre out exploring the sky. M15, the Swan nebula is a showcase object in Sagittarius and is one of the best, easiest nebula to see in the sky. It might be worth marking this one down to try out when its good to view.

Seeing as you are sky cruising Cass maybe try out the Pacman nebula, NGC 281 once the moon is gone and with your OIII. It might be pretty hard to see first time out but will tell much about your sky and filter.

In Cass I never miss viewing "ET" a fantastic goto asterism! I love this one.

[JOC]

6 minutes ago, jetstream said:

Swan nebula is a showcase object in Sagittarius

LOL, like that's an intuitive name pairing!!  I would love to be able to go out and identify all the constellations by eye.  I have bought a classically hand held constellation map / planisphere for this location.  Maybe I should get outside on starry nights and just familiarise myself with what's what.

Edited April 8, 2020 by JOC

[jetstream]

7 minutes ago, JOC said:

LOL, like that's an intuitive name pairing!!  I would love to be able to go out and identify all the constellations by eye.  I have bought a classically hand held constellation map / planisphere for this location.  Maybe I should get outside on starry nights and just familiarise myself with what's what.

Great idea!

I did the same- and still do- lawnchair observing can rule here lol! The constellations are actually the "map" of the sky and I observe them every time out. Can you make out Leo?

[JOC]

22 minutes ago, jetstream said:

Can you make out Leo?

No.

I can do, Orion/Betelgeuse and Bellatrix , The plough/big dipper and can find Polaris, baby plough/little dipper, the big W - which John says is Cassie, I can usually find the straight edges of Gemini/Castor and Pollux, find the winter pentagon of stars, but don't know the constellations that these are part of - though I know they take in several, Pleiades, and I tend to know which brighter planet is which in the summer, I know Venus in the winter and Sirius.  If I am callibrating the Goto I still need to use stellarium on my mobile to find out what the names of the brighter stars are to use and I've made every error it's possible to make on the SynScan GoTo units - the wifi dongle is far easier. 

See my EP's are really much too good for someone of my limited callibre.

[jetstream]

34 minutes ago, JOC said:

someone of my limited callibre.

You are not of limited calibre at all JOC- getting good views is a process at least it is for me. Having an open find can be very useful in all this I find.

So the constellations... in their full extent they can be boggling and frustrating to identify. I break them down a bit- take Leo, for example- a bright 3 star triangle with the point on the left- forget the rest for now. Try finding main stars in less than dark skies- just after dusk- and the main ones reveal themselves.

Some are huge like Cygnus and Aquila others more compact like Delphinius.

Leo is large in whole but the triangle is smaller.

So JOC we must all forget our limitations, realize where were at and explore! In my case galaxies need work, been at it 7 years now lol! startin to get better finally.

Hows your south view?

Edited April 8, 2020 by jetstream

[jetstream]

ps-there are DSC (sysnscan tricks) more later off to work on the waterline.

[JOC]

7 minutes ago, jetstream said:

Hows your south view?

Used to be excellent South, in the last year 5 spotlights have appeared about 1/4 mile away, still pretty good higher up.  Excellent East (over the estuary and then open ocean), West light pollution in distance, North Light pollution at distance and factory lights just beyond hedge - Polaris often awkward behind trees.  Whole garden ringed by trees, extra tall detached house central on plot limits views to about 2 directions in any chosen location.  Unless I want to lug everything 200m over un-made ground to the middle of the field where I can have a 360 degree view.

[jetstream]

4 hours ago, JOC said:

Used to be excellent South, in the last year 5 spotlights have appeared about 1/4 mile away, still pretty good higher up.  Excellent East (over the estuary and then open ocean), West light pollution in distance, North Light pollution at distance and factory lights just beyond hedge - Polaris often awkward behind trees.  Whole garden ringed by trees, extra tall detached house central on plot limits views to about 2 directions in any chosen location.  Unless I want to lug everything 200m over un-made ground to the middle of the field where I can have a 360 degree view.

Sounds vg, the ocean must be nice! I always try to observe south for some reason, actually SE to SW. You know, maybe try your filter out to see if it works and if underwhelming Astronomik and TV make excellent OIII- expensive yes but they work. Using a top OIII can mitigate light intrusion to some extent and Sag is so full of great objects.

Markarians Chain is easily do able with your scope in Virgo and so much more.

Synscan... the DCS's need a few procedures to help alignment- first you need a really solid, stable piece of ground- if the base moves around or wobbles no good. Second use a narrow FOV eyepiece after finding the alignment stars with the widefield. I forget if my AZ EQ6 has a 3 star align, if yours does I would use it.

Give it a try even in the moonlight to see if accuracy improves- the DSC can have a personality.

Hows the Morpheus on the moon?

 

[JOC]

The 6.5mm is well worth using on the moon.  You can nearly fall into the craters.

[Alan White]

Only just seen this post JOC, very nice set you have pulled together.
A matched set is always a pleasure to use and indeed look at too.
Enjoy your new one.