jetstream

Thank you for the honest report. I hope you get a chance to try the scope out under good skies. M31 shows detail, in particular dust lanes but for spirals try M51 under dark skies.

Gerry

I like that Portaball! nice scope

Well ... apart from the fact I can say I now own all of the current 1.25" TV Plossls (it's an OCD thing lol) ... my reasoning is that, if I've got my sums right, I will get a 3.14mm exit pupil on my 102mm Mak for a 32.5x magnification. It's the best I'll get on the Mak to utilise the Baader UHC-S filter on some nebulae, particularly M42.

Plus the 40mm will work well on the 235mm aperture SCT I plan on getting next year. 

Although the 24mm Pan gives me 54x it only gives me a 1.89mm exit pupil, which is fine, but it darkens the M42 nebula with the filter a bit too much for my liking. I found the 32mm Plossl gave a brighter image with the filter, although it was reduced to 41x. 

So, I would like to see how brighter it will be at relatively decent 32.5x with the Baader filter.

A few days ago I observed M42 with the 10mm Delos (unfiltered) and I could see the trapezium quite well. It looked great, but I was curious about how low a magnification I could get on the Mak as well. The 10mm gave me 130x which I think is probably the maximum decent magnification on a 4" Mak for M42. So the 40mm Plossl was a logical step for a useful low magnification on a f/12.7 Mak.

Great EP's Mak!

and....you have figured things out

Yes, I think you "outed yourself" on this one :grin:

Congrats Mike, this mirror will be superb.

ps your making me want a bigger dob already lol!

my moto is, if you die in debt you win how do you think im ordering my 20" 00 ultra grade mirrors. i win

Is the cat officially out of the bag now Mike?

right that's it.......

Moving Calvin?

 Big Dobs are easy

https://www.youtube.com/watch?v=nh00nv9wtqQ

?

Congrats for a job well done Damian! Your experience has been an enlightening one for me, the work and precision involved in making these mirrors is staggering.... Thank you for posting this thread.

Can't wait for your first light!

Is that you Quaoar? You have a big Webster if i remember...

At one of my dark sky sites the clouds will pick up the town's light dome 15 miles away- I now use this as a guide along with the SQM. The sites I use are the same darkness as laser_jock99's and vary almost exactly the same. The darkness changes with the seasons and on a truly dark, transparent night the Milky Way is a sight to behold.  The SQM is a valuable tool for astronomers and can identify dark zone edges in towns or cities in addition to finding remote dark sites.

Can we change the above to SQM-L and drop the "W" ?  thanks mods

Oh, that fast! Is it the same time for every magnitude?

And as Per sais, great DIY-project... even though i haven´t used mine that much

/Daniel

My SQM-L is faster the brighter the sky. The darkest I've recorded here was 21.8, with 21.7 being a very consistent reading. At this level of darkness it takes many seconds for it's reading.

I always give it 3 or so warm up readings first and then start measuring, mine says it is calibrated from the factory and it appears very accurate.

Damian, keep up the good work on the mirror. The thread is very informative- thanks.

Congrats for having some fine views Alan! I'd be pointing that scope at Virgo as soon as I could!

The LZ EOFB disappears when barlowed for some reason. Using the VIP at 1.5x eliminates a lot of it and @ 2x its gone. I notice this phenomena is more visible when I zoom in, to higher mag. The VIP barlow also helps the edge issues of the unbarlowed LZ in a fast scope, nothing noticed @ f7. The benefits of this EP far outweigh any of the mentioned issues IMHO.

At 1.5x barlow the LZ is a fine 5.9-12 zoom. Just my 2 cents worth.

PS- try it at 17.9mm on M42 under dark skies...

I do like the fact you can hold them under running water to clean them  To me the real advantage the purging offers is a higher resistance to frosting up in the winter. All 3 of my purged eyepieces are more frost resistant, which is nice for me here. Either inert gas works great for purging- and as far as reactive, unpurged atmosphere (oxygen) filled EP's would most likely corrode things first. In reality this isn't an issue either IMHO

Excuse to use cheaper gas and jack up the price...argon is a common inert gas. Not sure if I believe the seals hold better with argon...

Qualia,thank you for taking the time to put this together,it is fantastic.

I have at least a dozen refractors including a 102mm flourite, 127mm F15 triplet and a 220mm F 12.5 achromat, I still prefer the detail in my 16" SCT on a good night though a younger observer may well do better with the others.

Now that,Sir,is a telescope!(16" SCT) Mighty impressive looking,I can only imagine!

Very nice Rik,now we know who to ask about the Pentax's!Obviously they are excellent if they are in this case

I'm not one for excuses, but ....I've been suffering from chronic back ache this last week or so, a harsh case of sciatica. Refusing to take any time off work (exam time and slow but very worried children need to pass or they're put back a year!) mixed in with a little pain and a mighty cocktail of medicine is knocking me out a little. As soon as I get back on the mend, I'll tidy the OP and include a part III.

I am sorry and do apologise to everyone. Thank you all for your kind words and support, seriously, from the bottom of my heart, thank you to everyone

Your students are very fortunate to have you as their teacher Rob.Thanks again for all the work on this

Well done Qualia,can't wait for the DSO work!Thanks

For me "light tresspass" into my viewing area from local lighting messes up my night vision,so I take the steps to block that light,but actual skyglow problems are harder to combat. If the lights nearby are messing up nightvision and the sky is bright that is a real problem.I like umadogs reply!

There is also another thing that may help and it is the subject of exit pupil.As other posters have said as exit pupil decreases it dims the view.Mel Bartles assembled,came up with an interesting obsevation/conclusion.From the page Visual Astronomy at the Telescpoes Eyepiece:"Magnifying the image results in smaller exit pupils,the useful maximum magnification or smallest exit pupil being close to 1mm.The sky glow brightness drops more than 4 magnitudes to close to 26 magnitude as exit pupil shrinks to 1mm."This was from a reference of 21.5mag.The main issue for us (I think) is the 4 magnitude difference at the 1mm exit pupil.So thing is at the 2mm-1mm exit pupil will this provide an appropriate magnification for the existing sky (seeing ) conditions?I have personally obseved this from my light polluted house area.At 27x my scope illuminates the skyglow badly(3.28mm exit pupil),at 63x the skyglow is dimmed quite a bit(1.42mm exit pupil).This also answers my question of my Delos...Why at times did it do better on DSO's from my house?I thought just because it is a premium eyepiece,but at .86mm exit pupil the glow is dimmed to the limit.I can see bright DSO's from my yard-though not great-using the smaller exit pupils.So bascially if going to 1mm-2mm exit pupil puts you in a reasonable magnification range,try it.Along with the other suggestions this may help.