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Posts posted by Piero

  1. 30 minutes ago, jetstream said:

    The advantage to fast f ratios is eye illumination as you know and the larger aperture adds focal length. I like more eye illumination than f4.8 gives so for me on many galaxies I like 2mm-3mm but to pull cores out I go much lower.

    If I were going to buy another bigish dob it would be f3.5 and 18"-20"- so I could stand -no ladder. There would be much flexibility with such a scope and within Naglers PCII design specs. if money was no object Mike Lockwood would craft the mirror- this is his specialty and is perhaps the best at it. A JP Astrocraft cell would be enlisted as well.

    As always, astronomy has learning curves lol!

    You did well in designing your scope Piero.

    Thanks Gerry. 

    I also think that a lot depends on the skies on observes. Under my moderately light polluted skies, I like 2mm-1.5mm exit pupil as medium power eyepiece. That gives me a the best contrast for a large variety of targets. There is also a personal factor to add.. I tend to like a "jump" in magnification rather than small increments. For instance, the 20mm rarely saw the focuser as I tend to jump from 30mm to 12.5mm, and then I kick the VIP in to go to about 300x with the docter. Other people like larger sets of eyepieces so that they can fine tune. Different tastes!

    • Like 1

  2. 6 minutes ago, jetstream said:

    Thanks Piero, its like visiting old friends in the sky which I seem to do more and more. A small portion of the sessions are dedicated to exploring, including this one and some surprises do pop up such as near the Monkey Head- I do believe I got the best view yet of the Sharpless group SH2-254-258. I had seen some of this previously but tonight it was "in my face" with the new TV filters. Not sure if they had anything to do with it but the views were VG.

    I seem to be better at these diffuse objects over galaxies for some reason. The galaxy observing is coming along though and the Delos/PCII are working very well. This f4.8 scope likes a bit lower mag than the 10D/PCII gives on most all but the faintest of cores. A 12D would be VG and of course the Doc UWA is working well.

    Yes, clear skies to you!

    I just put your data in my calculator. 

    So the Docter with your 15" w/ PC2 gives 168.25x and 2.26mm e.p. 

    In my dob w/o PC2, the Docter gives 145.04x and 2.03mm e.p. W/ PC2, these # become 166.80x and 1.77mm e.p. 

  3. On 11/03/2020 at 04:15, Don Pensack said:


    I did not check the Paracorr setting for the 30mm APM UFF eyepiece because you find its setting the same way you find the setting using the ES HRCC:

    You use an eyepiece, any eyepiece, that you know the Paracorr setting for, insert the eyepiece, dial in the correct setting, focus the scope and lock the focuser

    (figuratively, i.e. don't move it).  Insert the new eyepiece and focus using the tunable top.  The setting that results is the correct setting for that eyepiece.

    So since I had been using a TeleVue eyepiece prior to using the 30mm APM, i simply inserted the eyepiece and focused with the tunable top.

    I didn't even bother to look at what the setting was since coma correction was perfect and stars at the edge were tiny pinpoints.


    Every time someone asks me what the Paracorr setting is for eyepiece X, I just ask if they have one eyepiece they know the correct setting for.

    If they do, they know the setting for every eyepiece because the tunable top parfocalizes all eyepieces that focus within the range of the tunable tops adjustment (0.7").

    Just focus using the tunable top.  Now, that won't give you extremely fine focus, which is why you still need to have a millimeter travel in the focuser.

    Thanks a lot for your very clear comment, Don. 

    I don't find coma distracting in my F6 dobson, but it is certainly there. I might invest in a PC2 in the next 15% TV discount sales, as I love refractor-like views.

  4. 17 hours ago, Nakedgun said:

    My first dob was a 10" Coulter Odyssey red tube that I bought used for $200 in the late 90s. I don't know if I have a photo anywhere, perhaps I'll stumble upon it sometime. Coulters had crude hardware, but that was the scope I used to gain my first view of Pluto at a star party near here known as RTMC (now defunct).  


    Having aperture fever at that time, I spent way too much money (just ask my wife!) on my then-new hobby by ordering this Starmaster 18, w/Zambuto f/4.3 primary, ProtoStar secondary, FeatherTouch focuser, and Sky Commander/Sky Tracker goto, as well. I saved some money by not ordering the transport handle option from Rick Singmaster and fashioned a pair myself (this did not assuage her).



    The heart of the beast: (transport box included with scope)



    Mirror cell:





    Operator's station:



    A relaxing pastime:



    The largest scope I will ever own, this instrument showed me a great many deep-sky wonders (blue supergiants in M31, no less), but after 16 years I finally grew tired of transporting it to dark skies, the setup and teardown (the mirror/cell in its box weighed 75lbs) and sold it off to a good home.

    Do I miss it? No question, but I have no regrets.



    Superb! That looks like an outstanding telescope. Thanks for sharing.

    • Like 1

  5. Never had issues in the second hand market here on SGL or ABS. In contrast three times I had issues with new equipment...1) TV plossl 20mm, 2) my first TV60, 3) my current 12" dob.

    The first item was kept as I wasn't aware of the issue that time. The second one was returned to the seller after I included a lawyer in the email communication. The third one was fixed by me after about 6 months of analysis, study, work, and testing. Now, THANKFULLY, it works and works very well, but it gave me quite some bad time!

    • Like 1

  6. 59 minutes ago, Ships and Stars said:

    I was going to say your best bet might be to have one made. Even for the SW mass produced dobs they seem pricey for what they are. It should bump contrast and help the mirrors stay a bit cleaner and fight off any dew, especially for the primary. I still need a secondary dew heater when it's really soupy out. 

    Thanks Robert, 

    I do have a light shroud but it has a few issues that I prefer not to state. Yes, a light shroud is very important, not only as a dew shield, but also for limiting tube currents and preventing things falling down to the mirror box! 



    • Like 1

  7. 12 minutes ago, John said:

    I used to use an Astrozap shroud with my Meade Lightbridge 12 inch. It worked well with that scope and was more or less essential with the amount of ambient lighting that I had around my observing site.  Not sure if Astrozap do one that would fit your dob though Piero ?

    Thanks John. :)

    I looked at astrozap shrouds and they are nice but it seems they make them for commercial scopes only.

    Teeter customise them, and they are not very expensive either. But this doesn't include customs..

    • Like 1
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