jetstream

Well.... If the central obstruction of the newt is around 20% the contrast loss is not noticeable (IMHO). Contrast is an interesting subject in itself as is the effect of central obstruction. Technically an optically perfect refractor will have less "contrast" loss than an optically perfect newt. The problem is there is no such thing as perfect optics and it is possible that an aberrated frac can have more "contrast" loss than a high spec newt, obstruction and all. Wheres @vlaiv?

Excellent reply Stu! My first scope was a 90mm APO that not only gives great lunar/planetary views it has proven itself on countless dark site trips, even showing IC434 before I knew what is was, no filter. This was under super transparent 21.8+ mag skies up north.

The other night I had to do some Rigel switching around so I put the cooled and collimated 24" Dob in the neighbourhood of Jupiter to line it up. Just so happens the seeing was excellent eventhough I was DSO hunting- go figure. With a 10mm Delos in the PCII the scopes mag was around 287x...and my jaw dropped to the ground once focused on Jupiter...yeah seriously, aperture opens up the detail a lot. At the other extreme is the TSA120 which I should have tested that night- this scope punches through the seeing like no get out and will support unlimited mag. Large aperture is hindered by seeing and possibly optics quality, but has the potential for more detail. Smaller aperture like APO typically have vg optics and punch through seeing more often than large aperture scopes. Excellent APOs can take seemingly endless mag. If you want to observe more often get the refractor, espc is seeing is more often avg (or worse) IMHO. Or like me get both a big dob and a refractor.

Yes 👍, the 15" was observing Pickerings Wisp with an empty filter slide the other night.

The C8 is regarded to be a fantastic all round scope, including neb observation. YKSE uses one with fantastic results.

Me too- it shows the Flaming Star in Auriga using the H130/24 ES 68 -a piece of cake. Dan McShane is a vg guy IMHO. Our DGM NPB is really good, very tight, good transmission.

Being in the USA go for the new Televue OIII- its my best OIII ( I have 3), not sure what they go for, I paid a couple hundred bucks from Astrosystems and he confirmed the specs for me. That extra test was not needed however as all these new TV filters are vg. $200 for a 2", expensive but worth it IMHO. Ive been ripped off before on filters...

No worries there thats for sure- Astronomiks are vg and tightened up there bandwidth a few years ago.

The view is washed out with the OIII?

I've played around extensively with exit pupils and filters. Exit pupil definitely matters IMHO.Yes 2mm is very small for OIII's- I like 4mm-6mm . As an example I used a 30mm ES 82 @ f4.8 the other night for a 6.25mm exit pupil on the NAN for those 2 features. The 20mm APM 100 was also used at 4.2mm with good effect. From dark skies a 4mmish exit pupil works great on the Veil - but- I find aperture matters and not for the commonly thought reason. A large scope with a long fl needs less "help" bringing out features as the mag is already high enough. A small scope can take a bit more mag with the filters- a trade off will be found between exit pupil and the needed mag. The darker the skies only lead to greater enhancement regardless.

I'm thinking your darker than "Bortle 6 " suggests. OIII filters work well espc when you can see the objects unfiltered and there is no better filter for the Veil than a top OIII IMHO.

I understand your points Don and an agree -with a caveat- and that is sky conditions. Under truly dark skies the UHC is reached for first many times- actually I just flick the filterslide back and forth to compare. Under less than dark skies the additional "contrast" provided by the OIII is a big asset.

100% agree. Get a good OIII first IMHO.

You saw these no filter, vg- how dark is your sky described as Bortle 6? NELM or SQM any idea?

Some of us use low power 100 deg eyepieces for filter use and finding galaxies etc, espc in a 14" dob at f4.6. The 9mm APM will be a good higher power galaxy viewer eventhough many use a bit different spec eyepiece for this observing (and many dont...) The Delos/Pentax XW are very highly recommended for this and also provide sharper views on the moon/planets than the 82/100 deg EP's (IMHO). The 20mm APM is hard to beat for a low power eyepiece in this planned scope- throw in a couple of Delos and all set- I love spending others money lol! ps a top UHC/OIII will be a huge benefit- Astronomik or new Televue IMHO.

Well the 2 features mentioned are still there... 👍 Conditions were ok but trans was down. The MW had light structure, not horizon to horizon but was not bad at zenith. No stars visible till about 10 deg above the horizon and M31 was easily visible but subdued and not the bright streak it is under better conditions. No M33 naked eye. Trans worsened during the session so I came back in. The 15" was used and the NAN was visible no filter but not the best, I used the UHC to bring out the features and the one is next to that cluster, the other coming in near the first. I figured Id try under these conditions to illustrate that super good conditions are not needed. What is needed IMHO is the MW to be easily visible at zenith and with a bit of washed out structure. Eagerly waiting reports!

I dont believe its either, Ive never seen the features named. These 2 are challenges for sure but under the right conditions with the right eyepiece for the scope they are not bad. Eagerly waiting reports!

Here is a borrowed image that marks the 2 challenge features I'm talking about. Years ago at least one other SGLer observed these- anyone else since? I hope its ok to use the image for this illustration.

If you get cold weather, like me in north ontario the focuser will tighten up nicely and work when most dont. The plumbers tape is a good solution, with lots of wraps.

👍 I do this myself and focus with the PCII after setting it up on "A" and focusing the 21E after which I lock the focuser. Good enough for me.

Its amazing the lengths we go to with regard to collimation only to have tolerances sneak up on us- I tighten the focuser screws in the same order on the eyepieces as I do on the laser lol! My Moonlights are pretty good for consistency though.

I have to say that this objects has surprises- the 24" shows bright spikish "crab" features in the 24"- the 15" under the best conditions here will start to reveal them faintly. Bottom line is to enjoy the hobby and continue with pursuits regardless of conditions IMHO. I hope you have a great trip Iain!

This is a good thing, but these days I just try stuff- like Einsteins Cross in the 24"-bit off more than I could chew (so far) but I'll keep trying, got the lensing galaxy anyway. These skies are similar to mine- I vary between 21.4 and 21.9, with avg around 21.7 and at 1100' above the sea. For sure take your scope IMHO, there are lots of targets that will wow from home regardless.

I dont put much into limiting mags, espc with objects like HII "knots". I have zero doubt that you will see some of these from truly dark skies- my 8" dob does...Yes 20.4 wont do it most likely, every little bit over 21 helps... You ever go on dark site trips?

Are you sure? The C8 is a very capable instrument...what eyepieces do you have? Never say never... espc with respect to M101 and M33...