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The Year-Long 60mm Telescope Challenge

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#26 Astrojensen

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Posted 07 April 2013 - 03:33 PM

BTW, I was reading through Jim's list, when I discovered that it's slightly less than 50 pages long, not 65, as the DSO part is listed twice... It begins anew on page 49!


Clear skies!
Thomas, Denmark

#27 Astrojensen

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Posted 07 April 2013 - 03:34 PM

I had planned to try some difficult solar system objects as well, such as planetary satellites and minor planets. Any interest?


You bet! Go for it! :jump:


Clear skies!
Thomas, Denmark

#28 Astrojensen

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Posted 07 April 2013 - 03:49 PM

More important than the "absolute" rating, however, is whether the "relativity" of the ratings is accurate.



It isn't. I've looked at the list and how can it list a NAKED EYE STAR CLUSTER such as fifth-magnitude M41 as "Difficult"???? And M35 is only "detectable"... In a 60mm? And there are literally dozens of such examples.

To me, at least, "detectable" means something is very, very faint and barely visible with great effort, it is beyond challenging, shows no details other than a very faint smudge, perhaps with some elongation, but no other details. We are talking naked eye open clusters here, for spaghetti's sake.

But I guess I need to walk the walk and not just talk and talk and actually come up with a better list.


Clear skies!
Thomas, Denmark

#29 Chuck Hards

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Posted 07 April 2013 - 03:55 PM

It should be remembered that "difficulty" can be considered a moving target. Aperture aside, image scale (magnification and field of view) can play a huge role in how visible an object is. Something that is borderline in a small telescope can suddenly become almost obvious if the right eyepiece is used. One of my first "discoveries" as a rank beginner all those decades ago.

It's part of the challenge. :)

#30 jrbarnett

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Posted 07 April 2013 - 04:28 PM

Bah! Formatting. Moving ST3 data into MS-Word tables. Part of the double star list, too, is duplicated I see. Sorry. I can update it on Monday. All Mac OS X at home; no Sky Tools.

However, the list is the list for this exercise. As clearly stated in the article, this is *not* supposed to be a comprehensive list of everything you can see in a 60mm telescope, nor is there any guarantee that it's possible to see everything on this list in a 60mm (many targets will, indeed, be *very challenging* even factoring in ST3's pessimistic rankings). From the article:

"Below is a carefully considered list of targets that *may* be within reach of a 60mm telescope to a middle-aged experienced observer under typical suburban skies. The list was constructed using thoughtful, deliberate filtering in SkyTools 3 normalized for my home observing site at 38N. It does not necessarily list every target potentially visible in a 60mm. Nor is every target on the list necessarily visible to anyone, anywhere, in a 60mm telescope."

The objective of the challenge is NOT to assemble a 60mm "best targets" list. Rather it is to push participants to try and find the limits of a 60mm telescope and, hopefully, come away with the sense that 60mm is larger and more competent than they expected or, if they cut their teeth with such a scope, more capable than they remembered .

Regards,

Jim

#31 jrbarnett

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Posted 07 April 2013 - 04:49 PM

Or maybe the "Urban Observers Program". :grin:

Here are the 60mm scopes I plan on using for the effort:

Posted Image

Posted Image

Posted Image

Posted Image

Posted Image

Granted the mount is a bit nicer than the one that my old Jason came with. :grin:

Regards,

Jim

#32 Astrojensen

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Posted 07 April 2013 - 04:54 PM

It should be remembered that "difficulty" can be considered a moving target. Aperture aside, image scale (magnification and field of view) can play a huge role in how visible an object is. Something that is borderline in a small telescope can suddenly become almost obvious if the right eyepiece is used. One of my first "discoveries" as a rank beginner all those decades ago.

It's part of the challenge.



Absolutely true.


Clear skies!
Thomas, Denmark

#33 Astrojensen

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Posted 07 April 2013 - 04:55 PM

Jim, that's an incredibly nice setup!


Clear skies!
Thomas, Denmark

#34 Astrojensen

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Posted 07 April 2013 - 05:05 PM

As clearly stated in the article, this is *not* supposed to be a comprehensive list of everything you can see in a 60mm telescope



Such a list is incredibly difficult to make, since the observer's skill is a moving target and with increased skill, you can see fainter and fainter objects, so the list needs to get bigger and bigger. It was in no way my intention to suggest that your list was trying to be a comprehensive list of objects for a 60mm.

But I still thinks it needs to be scrutinized and the errors removed. Some of them are genuine catalog errors, such as stars instead of galaxies and such. That PGC galaxy in Andromeda is a star, for example.


Clear skies!
Thomas, Denmark

#35 jrbarnett

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Posted 07 April 2013 - 06:30 PM

Actually perhaps flagging the errors in the list would be of assistance to the Sky Tools 3 author as the classifications are all based on the designations in the application. :question:

Regards,

Jim

#36 Astrojensen

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Posted 08 April 2013 - 01:59 AM

Actually perhaps flagging the errors in the list would be of assistance to the Sky Tools 3 author as the classifications are all based on the designations in the application.



Good idea.

BTW, I am working very early in the morning this week, or else I would be out there with the 63mm, bagging stuff from the list. I have a day off today, but of course it was cloudy yesterday evening.


Clear skies!
Thomas, Denmark

#37 yashi

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Posted 08 April 2013 - 09:22 AM

awesome idea :)

#38 jrbarnett

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Posted 08 April 2013 - 09:54 AM

Thank you yashi.

I'm have an updated 60mm Challenge List, modified to remove duplications in both the double star and DSO sub-lists. I'll see about getting the version embedded in the article replaced with this one. 33 pages is more manageable than 65. :grin: Unfortunately it is too large to attach to forum posts, even if I publish it as two lists; one for multiples/doubles and another for DSOs. In the meantime, if you would like the updated list in either PDF or Doc format, let me know by PM and I will e-mail it to you.

I should also clarify that the difficulty rating scale for DSOs in ST3 ranges like this, from easiest to hardest:

Easy->Obvious->Detectable->Difficult->Challenging->Very Challenging

One other thing to bear in mind is this. The list was generated using the optimal date for a Messier Marathon as the reference date in the tool. When the complex difficulty rating model is applied to the filter data, including this date at my site, targets that don't get out of the soup will reflect a higher difficulty rating than they would at a time of year where that target is at or near the meridian.

The difficulty ratings are only one guideline. Using the stated magnitude, too, may be helpful. I can also generate and provide custom formatted tables with other information columns (alternate names, dimensions of object, relative surface brightness, etc.), but went with the format in the article for simplicity. PM me if you'd like a different cut of the data.

EDIT: I've attached the updated list with redundancies eliminated to this post in Rich Text Format. Everyone should feel free to do whatever you like with the data table and its format.

Regards,

Jim

Attached Files



#39 Jim Romanski

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Posted 08 April 2013 - 10:07 AM

What fun! Nice idea Jim. I never had a small refractor as a kid. I started out with a 100mm Celestron SCT that my Dad let me use.

I do remember fondly a camping trip to the Black Canyon of the Gunnison in Colorado. It was extremely dark in the Canyon. M6 and M7 were ablaze it seemed. All I had was a 7x35 Fujinon binoculars. I was surprised to be able to sweep up about 35 Messier objects just sitting at the picnic table. Even the little globulars under the Teapot in Sagittarius at 7X. Dark and dry skies can do wonders for your observing.

Not sure what instrument(s) I'll use. Gotta knock off 3mm from my AT72.
So what if you use a 60mm refractor and mount a really BIG eyepiece on the other end. But then you look through the 60mm objective and out through the eyepiece...would that be cheating? :tonofbricks:

#40 dermarkus

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Posted 08 April 2013 - 10:10 AM

I love that idea. I do not own any 60mm scope, but plan to use my 80mm refractor stopped down to 60mm instead.

Jim, is there any chance that you can provide that list in a format that can be imported into a spread sheet ? I was not
able to do that with the PDF.
The spread sheet would allow me to sort the objects differently. I live on 51 deg latitude and i will not be
able to see some of the southern objects. Sorting them allows me to filter on declination for example.

Thanks
Markus

#41 jrbarnett

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Posted 08 April 2013 - 10:30 AM

Funny you should mention the really big eyepiece on a 60mm. In my picture of my two 60mm scopes on an alt-az mount, the AT60EDT on the left has a 40mm Sterling Plossl (a little over 5-degree TFOV :o ) loaded in the diagonal.

When I was taking the pictures, I noticed that there was a lovely view of the sky and clouds overhead when looking into the objective, so I'd say no, so long as the eyepiece has an eye lens no larger than 69mm in diameter, it isn't cheating. :grin:

It also occurs to me that using the "Herschel Principle" (i.e., once you spot a target in a larger scope, your chances of seeing the same object in a smaller scope are better), participants using an aperture mask on a larger instrument may also have a decided advantage. Specifically they can locate and observe the target at full aperture and then put the mask in place to see if they can still detect it at the smaller aperture. IMO, that is not cheating either.

Because I will be using a side-by-side configuration for my 60mm scopes, provided that I align each saddle, I'll have the opportunity to put a 60mm on one side and a larger instrument on the other, and work back and forth between them. For especially challenging targets I may do something like that.

Regards,

Jim

#42 jrbarnett

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Posted 08 April 2013 - 10:42 AM

Hi Markus. I just updated post #5785633, above, and attached a Rich Text Format version of the cleaned up list. That should be pretty easy to dump into a spreadsheet. I had to select a skinny font and low point count to minimize the size of the attachment, so you may want to update the font size as well as the font itself for readability before moving it to a spreadsheet.

Regards,

Jim

#43 CharlieB

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Posted 08 April 2013 - 11:47 AM

I'm well armed in the 50-60mm scope range, so I plan on participating as much as New England will allow. This will be a fun project.

#44 Chuck Hards

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Posted 08 April 2013 - 12:12 PM

The objective of the challenge is NOT to assemble a 60mm "best targets" list. Rather it is to push participants to try and find the limits of a 60mm telescope and, hopefully, come away with the sense that 60mm is larger and more competent than they expected or, if they cut their teeth with such a scope, more capable than they remembered .


Exactly. In fact my motivations are pretty selfish; I just want to see what the little scope can do now that I have decades of observing experience under my belt. Any contribution to cleaning-up or establishing some kind of list is a very distant second. I'm doing it just for fun.

#45 droid

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Posted 08 April 2013 - 12:43 PM

so there is a new pdf, or the original has been modified?

#46 jrbarnett

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Posted 08 April 2013 - 01:25 PM

I eliminated target duplications that Thomas noted in the original pdf list embedded in the article, and attached a Rich Text Format updated version of the list a few posts up in this thread. I'd also like to update the pdf in the article and have sent Charlie an e-mail about the feasibility of doing that.

Regards,

Jim

#47 Astrojensen

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Posted 08 April 2013 - 03:11 PM

I should also clarify that the difficulty rating scale for DSOs in ST3 ranges like this, from easiest to hardest:

Easy->Obvious->Detectable->Difficult->Challenging->Very Challenging



Oh, that suddenly makes the difficult rating a lot more meaningful.


Clear skies!
Thomas, Denmark

#48 jrbarnett

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Posted 08 April 2013 - 09:48 PM

I'm with you Thomas. The difficulty level names aren't necessarily logical or intuitive, but that's the way they rank in the application.

Incidentally, I also looked at a few 60mm to 70mm currently available scopes that might be nice options. The Meade NG-60 runs about $80 and looks like a modernized iteration of the classic alt-az mounted beginner's 60mm achromat.

A Vixen 70lf or Meade NG-70 or, stopped down a millimeter or two, also, might be an option as well.

I'm sure there are other options too.

Regards,

Jim

#49 Astrojensen

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Posted 09 April 2013 - 03:45 AM

Incidentally, I also looked at a few 60mm to 70mm currently available scopes that might be nice options. The Meade NG-60 runs about $80 and looks like a modernized iteration of the classic alt-az mounted beginner's 60mm achromat.

A Vixen 70lf or Meade NG-70 or, stopped down a millimeter or two, also, might be an option as well.



I've compared my 63mm Zeiss and my 72mm WO ED and the 72mm is quite noticeably brighter, giving it a real advantage on faint objects. If this is supposed to be a challenge for 60mm scopes, you should probably limit the max allowed aperture to ~65mm - 66mm (I am being completely selfish here, as this would still allow my 63mm Zeiss! :grin: ). A 66mm aperture would also allow the modern 66mm ED's and apochromats to participate.


Clear skies!
Thomas, Denmark

#50 jrbarnett

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Posted 09 April 2013 - 09:57 AM

Yup. The range permitted in the article is any aperture from 60mm to 69mm, so the Zeiss is definitely a valid tool for the attempt based on the guideline.

In fact, I would even accept a well-constructed argument that a considerably larger catadioptric (such as a 90mm MCT) was inefficient enough to deliver actual light grasp on par with a much smaller unobstructed scope. If folks want to come up with a calculation of equivalent unobstructed light grasp for small catadioptrics, I'd have no objection.

If I do this with my Celestron C90 (aluminum with SiO2 overcoat on primary and secondary, multi-coatings front and back on the corrector) here's what I come up with: 90% reflectivity for each mirror surface, 99.5% transmission for each surface of the corrector (the corrector is not XLT coated, but rather standard Synta multi-coated), and a secondary obstruction of 10% by area, I get something like a 75mm fully multi-coated refractor equivalency. You'd still need to stop the average 90mm MCT down to meet the requirements, but by something more like 7-8mm rather than 30mm.

Regards,

Jim


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