oldfruit

Great read, loved your report and having recently acquired a 20 inch dob myself, I can totally relate to the experience. Aperture under the right conditions really does allow you to go deep and reveals structure and detail in objects that were smudges when observed previously.

A colleague from our local club remarked that he had never seen the Veil Nebula in such detail, I had to agree.

Wishing you many more cloud free nights.

Mark

There are many areas that now turn off street lights after midnight. Whilst this might not be ideal it does present us with an opportunity to observe from home under minimal light pollution and may solve the issues you are experiencing with the street lights?

Mark

I Have not read the entire thread.

I have dabbled in both visual and astrophotography. I have enjoyed them both for different and also similar reasons.

When imaging you can reveal far more detail than you are able to pick out visually, Also you can more readily share your results.

You can only share your results visually if you are observing with a colleague

I came to a bit of a crossroads recently where I wanted to make a substantial purchase. I could have bought myself a decent imaging rig or a large dob. I opted for the large dob as I love being out under clear dark skies, hunting out obscure faint fuzzies which I have found with my eyes, no go-to, no motor drives, just good old fashioned visual astronomy. I have had and been fortunate enough to share some "wow" moments when observing visually and am hopeful that they will keep coming since I have upgraded my scope.

I think it all comes down to personal preference but for me and most of our club, visual all the way.

I have to agree John, whilst it may be present it is not too bothersome and probably not so noticeable to my inexperienced eye. At F/4 it was glaringly obvious, hence the initial enquiry.

11 hours ago, John said:

Was that with the F/4 20 inch Mark ?

Are you going to use the Paracorr with your 12" Revelation F/5 ?

It would be interesting to see how much the slightly slower focal ratio benefits from coma correction.

 

Yes it was with the 20 inch, not used it in the 12 inch yet but at F5 coma was much less of an issue, though still present.

3 hours ago, jetstream said:

@oldfruit I hope sidetracking your thread a bit is OK, I don't mean to de rail your paracorr purchase/experience.

Not at all.

The more input and information the better.

Hi and welcome, also in Lincolnshire.

I am happy to report that I managed a short observing session the other night and wow, what a difference a Paracorr makes. Using a 28mm Skywatcher Nirvana I used the middle setting on the Paracorr and with a slight tweak it was great, flat field almost to the edge with minimal coma on the very edges of the FOV.

I can see that my observing experience will be much improved in the coming months.

Thank you all for the help and advice.

Mark

6 minutes ago, Don Pensack said:

There is an empirical way to find the right setting for an eyepiece.  You only need to do this for 1 eyepiece.  For every other eyepiece you own or will own, you simply insert the other eyepiece and focus using the Tunable Top.

Whatever setting results is the correct setting for that eyepiece and you can pre-dial it before you put the eyepiece in in the future.

So, Insert the eyepiece with the tunable top set to its maximum out setting (H).  Focus the scope and look at stars at the edge of the field (or move a moderately bright star to the edge of the field).

Still see coma in the star image?  Then dial the top in one setting to G , focus the scope and repeat your evaluation of a star at the edge (it's easier to see coma on a brighter star, like Polaris, than a dimmer star).

Still see coma?  Keep moving in one setting until, when you focus, the star at the edge of the field displays no coma.

That is the setting you'll use for that eyepiece in the future.  For every other eyepiece, leave the focuser where it is and focus using the tunable top.  Write down the settings so you know what they are.

You can do this with any eyepiece from any company.  If the eyepiece needs more outward movement of the tunable top, you can add a parfocalizing ring to the eyepiece to raise it a bit.

If the eyepiece needs more inward travel of the focuser, you will have to settle for the inward most setting (A): example Nikon HW 17mm.

What you do by doing this is to set the Paracorr in the light cone from the primary.

 

There is one more way to do this: insert the Paracorr in the focuser in setting E.  Place translucent scotch tape across the opening of the Paracorr in an X shape where the eyepiece would normally go.

Point the scope at the moon and focus the telescope with the moon's image on the translucent tape.  When the Moon is in focus, you have found the perfect setting of the Paracorr in the light cone from the primary mirror.

Lock the focuser in this position, and insert each one of your eyepieces in sequence, focusing on the Moon with the tunable top.  The settings each eyepiece uses is the correct setting for that eyepiece.

 

I have done both and am happy to report that, at most, I was about a half setting off on an eyepiece or two that way, and a half setting is a very small error (about a mm).

 

The problem with both methods is if the observer is nearsighted.  In that case, perform the test(s) with glasses on that correct your vision.  Otherwise the settings for each eyepiece will be off.

Later, when you view without glasses, the distance between the eyepiece and Paracorr will have already been accurately determined and even if you have to move the focuser in to focus, the correction

will be approximately correct.

Many thanks, I will try both methods.

Mark

28 minutes ago, jetstream said:

I hope you get this sorted out Mark!

my motives are insideous though.... as I'm in the same boat lol! 😀

What distortion? just coma or other stuff?

Hi Gerry,

It is just the coma. In my f5 the Nirvanas performed reasonably well and coma was limited was not too much of a distraction and I could live with it. Having started using an f4 I can immediately see the difference. The middle of the field of view is lovely and bright and sharp, however coma is now really noticeable in the outer parts of the fov and whilst I do not find it too bothersome, having the Paracoor can potentially enhance my experience at the eyepiece. I am sure that with all the great advice given I will find the improved observing experience reasonably easy to achieve. (Fingers crossed)

Mark

Thanks Richard, In the absence of a definitive list that sounds like a good method to try.

Mark

Hi,

I am currently using an f/4 dob and as part of the purchase a Televue Paracorr type 2 was included. I have not used the Paracorr yet and I am noticing greater distortion than when I was using an F/5. Naturally I want to get the most out of my observing.

As I am not currently using Televue eyepieces, is there a guide out there somewhere as to which settings would be used for different eyepieces? My eyepiece collection is mainly Skywatcher Nirvana`s.

Thanks.

Mark

It is always encouraging to read report such as yours as it gives me things to look forward to. Having made a substantial step up in aperture recently I am getting a good idea of what to expect. Just waiting for the darker nights..

Considering the conditions I think you have done well.

What a great read and a fantastic piece of work.

Cannot wait for darker skies to return.

5 hours ago, jetstream said:

I didn't realize you had a big dob as well- what scope?

For me the step up from the 15" was a very noticeable one on galaxies in particular. I still cant get over the views of the Swan neb and the Eagle neb through the 24", I had no idea that these would be so enhanced over the 15" (& its no slouch). I eagerly wait M42!

It was made by a chap called Bob Sutton who unfortunately passed away recently and is modelled on an Obsession telescope. The scope is approx 13 years old and the primary was recoated with Orion Optice Hi Lux coatings late last year.  The optic were sourced from Markus Ludes (APM) and are either Lomo or Intes Micro optics and is what I call "my forever scope" as I do not think I will ever manage to negotiate that well with the wife again!

I am also waiting for the darker nights as I have had first light with the scope but conditions are less than ideal this time of year so I have not had the chance to see how deep the scope will go, but if first light is anything to go by I am in for a treat.

Really interesting read and good to get an idea of some potential targets for the season ahead. It is reassuring to know that existing objects take on a whole new wow factor using a large dob, and galaxies that were not visible previously are now within reach.

I picked up a 2 step stepladder for £5 at our local car boot.

Me too Ron!

I am sure I will, enjoy revisiting old targets that will take on a new perspective, seeking out subtle colour in objects that looked neutral previously and seeking out those faint fuzzies that we all enjoy. Just considering eyepiece choices now as I have recently slimmed it down somewhat.

Considering the conditions there is a lot of detail , the belt around the GRS seems to have faded somewhat. Nice capture.

Thank you guys, needless to say I am chomping at the bit to get the scope set up and out under a clear sky. As the scope has barrow handles I was thinking of buying an 8X6 shed to house it in and leave it set up. Should be able to just wheel it out when in use. Can`t wait, thanks for all the suggestions.

I will be sure to post a first light report and if your comments are anything to go by first light will be a revelation. Previously I was using a 12 inch dob so quite a jump. A colleague has a 16 inch flextube which gives impressive views.

M13 should be impressive, M57 looks good through my 12 inch dob so will be interested to see what difference the new scope makes. The thought of seeing the spiral of M51 instead of using averted imagination is exciting. Typical that we have a week of rain now!

I have just been fortunate enough to purchase a 20 inch F4 dob with a type 2 paracorr.

I was wondering if anyone with a similar setup could advise of expectations and give some new targets to look out for?

Thanks,

I agree. I have often referred back to the observation target pages in the magazines.