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XT8 Plus - PAINFUL to find M80!

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#1 StarWager

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Posted 01 August 2020 - 03:24 PM

Last night I was looking for M80 from my backyard, and had several things going against me.  1) I am in a light-polluted area, and can only see 3 stars in Ursa Minor.  2) The moon was bright in the South.  3) The seeing was not particularly good ... brighter stars were not resolving to a sharp point but remained slightly fuzzy at moderately high power.

 

FIRST, I hunted M80 in my brand new (to me) 80mm APO with manual EQ mount.  (Am still learning this scope.)

This took me maybe 10 minutes or less from consulting the star chart, to hopping in the finder scope to the right location, looking in the EP in that area ... repeat about 3 times.  Found it at 102x as a small smudge.

 

Then, I wanted to see M80 in my 8" Dob.  Long story short - I NEVER FOUND IT. 

 

Here are the main issues I see with my Dob, when looking for a "small faint smudge" that needs 100+ power to find in my light-polluted skies.

  1. I have come to believe that the red-dot finder kinda sucks.  It does not allow seeing more stars than my un-aided eyes.  So for example, I could not see Omicron Sco (mag 4.6) with my eyes or the red-dot finder.  I was left trying to "hop" starting from the visible Al Niyat to Omicron to M80, using the EP to validate the hops and directions.  Also, the red "dot" itself is a large slightly out of focus "sort-of dot" ... it definitely does not help find things like my APO's 6x30 finder scope with cross-hairs.
  2. Trying to "nudge" the XT8 Plus with finesse and accuracy, in the right direction, across a distance of more than a couple FOV's, feels kinda like an exercise in futility. The slow motion controls on an EQ mount are far better for this.  In order for the Dob to be stable at high power, and not move accidentally too far in the altitude aspect, I need to at least somewhat tighten the tension knobs.  But then smooth movement becomes difficult to manage.

Note I do not want to get a Go-To scope to solve the issue of finding things.  I want to learn the skies.  Is a manual Dob simply not the right scope, for a goal of observing all 110 Messier objects, from a light-polluted area?

 

thanks much!

scott



#2 The Ardent

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Posted 01 August 2020 - 03:35 PM

M80 is not for moonlit skies.
Without the moon I can see it with 10x50 binoculars.
I recommend a Telrad/Rigel AND a 50mm RACI Finder.

Many years ago when I had the XT6, the stock finder was useless. Added a Telrad and badda-bing was able to center targets in seconds. many new ones not attempted before.

I remember a full moon night attempting several DSO’s and seeing some easy- like M8 and M57

Nice thing about these dobs: easy to attach things to the metal tube. If you add a finder like the Telrad use some non-permanent attachment first, to see what placement works for you.

Back to M80- Ask yourself : What two bright significant naked eye stars does M80 lie directly between?
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#3 Dana in Philly

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Posted 01 August 2020 - 03:37 PM

Don't fault your XT8. Try again when it's a new moon. That moon was very bright last night, and would've washed out any DSOs in Scorpius.


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#4 cuzimthedad

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Posted 01 August 2020 - 03:38 PM

Many, many amateur astronomers start out with 8" dobs as their first scope. I personally cannot stress this more...practice and patience are necessary to making it through this hobby. Finding a dark sky site you can travel to on occasion, helps make those frustrating backyard ones seem more tolerable. I would read about mods others have made to their dobs to make observing better. But the more time you spend with your scope, the more comfortable you'll become with it. Practice different tension settings, maybe buy a small finder scope or Telrad for it. You will "get it" at some point, observing will become second nature.


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#5 Dana in Philly

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Posted 01 August 2020 - 03:40 PM

+1 The Ardent.

 

Get a Rigel or a Telrad. When the stars begin to come out, point your scope at Vega (this time of year, it'll be among the first to show up), center it in your scope, then calibrate the finder so finder and scope are both centered on Vega. Then you're good to go. Study your star chart, figure out where M80 is, use the Rigel or Telrad to get yourself pointed there, and then take your time and you'll see it. It'll be faint, but it's beautiful. Use averted vision.


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#6 JohnBear

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Posted 01 August 2020 - 03:53 PM

Red Dot Finders (RDFs) have their realm of good use, but it is definitely not universal. You will probably find either the Telrad or a Rigel reflex finders an improvement - but they also aren't suitable for "everything". 

 

Probably the mosy useful finder for your dob will be something like an 8X50 RACI scope finder - but they won't do everything. I think most med/large dob owners eventually end up with several finders that they use in sequence. The red dot or reflex finders are good for getting to the close "neighborhood" of you target Then a 8X50 scope finder gives you some magnification to help you precisely locate and center your target - then you move to the eyepiece and view it. RACI scope finders are preferred over "starlight-thru" finders because you don't have crane your neck so much to look thru it.

 

Zoom EPs are also helpful by allowing a low-power, wide view to find and the object; then you can easily zoom to a higher magnification without having to change EPs (during which time the target rotates out of your narrower field of view). tongue2.gif

 

Find and visit some astronomer friends with a similar size dob and see what they use. Buying based in online catalog descriptions (or posts in a forum) is not quite as informative as seeing and using the real thing!  waytogo.gif

 

As for "Following" targets with a dob - it is a quickly learned skill (be patient). It also needs to be reasonably maintained so "stiction" is Just Right for Alt & Az adjustments. Dob scopes also need to be "balanced" properly for good manual tracking.  Search for those terms to learn more.

 

Hope this helps!


Edited by JohnBear, 01 August 2020 - 04:01 PM.

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#7 gwlee

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Posted 01 August 2020 - 03:56 PM

Last night I was looking for M80 from my backyard, and had several things going against me.  1) I am in a light-polluted area, and can only see 3 stars in Ursa Minor.  2) The moon was bright in the South.  3) The seeing was not particularly good ... brighter stars were not resolving to a sharp point but remained slightly fuzzy at moderately high power.

 

FIRST, I hunted M80 in my brand new (to me) 80mm APO with manual EQ mount.  (Am still learning this scope.)

This took me maybe 10 minutes or less from consulting the star chart, to hopping in the finder scope to the right location, looking in the EP in that area ... repeat about 3 times.  Found it at 102x as a small smudge.

 

Then, I wanted to see M80 in my 8" Dob.  Long story short - I NEVER FOUND IT. 

 

Here are the main issues I see with my Dob, when looking for a "small faint smudge" that needs 100+ power to find in my light-polluted skies.

  1. I have come to believe that the red-dot finder kinda sucks.  It does not allow seeing more stars than my un-aided eyes.  So for example, I could not see Omicron Sco (mag 4.6) with my eyes or the red-dot finder.  I was left trying to "hop" starting from the visible Al Niyat to Omicron to M80, using the EP to validate the hops and directions.  Also, the red "dot" itself is a large slightly out of focus "sort-of dot" ... it definitely does not help find things like my APO's 6x30 finder scope with cross-hairs.
  2. Trying to "nudge" the XT8 Plus with finesse and accuracy, in the right direction, across a distance of more than a couple FOV's, feels kinda like an exercise in futility. The slow motion controls on an EQ mount are far better for this.  In order for the Dob to be stable at high power, and not move accidentally too far in the altitude aspect, I need to at least somewhat tighten the tension knobs.  But then smooth movement becomes difficult to manage.

Note I do not want to get a Go-To scope to solve the issue of finding things.  I want to learn the skies.  Is a manual Dob simply not the right scope, for a goal of observing all 110 Messier objects, from a light-polluted area?

 

thanks much!

scott

I learned to star hop with an 8”f6 Dob in a big metro area that was a white/red zone.  Last night the moon would have made finding DSOs more difficult than it would ordinarily be from a light polluted site. From a light polluted site, a 50mm optical finder would be my first choice, and a red dot finder would be my last choice, and the Orion red dot finder that often comes with that scope is among the worst of the worst. 

 

Orion makes a 9x50 finder for your scope that I found works better than your 6x30 from a light polluted site. It weighs ways about twice a much though, so you might need to add some weight to the mirror end to counterbalance a 9x50. I recommend using your lowest powered EP to find objects (or the field where you expect to find the object) and then switching to a higher powered EPs to see gives a better view. 
 

From a dark rural site, I prefer a Telrad for star hopping, but it didn’t work as well for me as a 9x50 in a brightly lighted city. It takes some practice to learn how to nudge a dob along, but it becomes easy with practice. 


Edited by gwlee, Yesterday, 11:03 AM.

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#8 ShaulaB

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Posted 01 August 2020 - 04:02 PM

Try a lower magnification. The larger aperture scope will pull it into the eyepiece at 60x. Then pump up the power.
Another vote for a Telrad.
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#9 JohnBear

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Posted 01 August 2020 - 04:16 PM

BTW - you might want to look into making your Dob a manual "Push-to" (rather than Go-To) by simply adding an Az setting circle and using a low cost digital angle finder.  That is a fun, easy, and inexpensive DIY project way of pointing your scope right at a target's coordinates with almost the same accuracy as a go-to (only quicker, easier, and much less expensive). There are extensive posts on this in the ATM/DIY forum. 

 

Also +1 for dark rural sites.  That will make a great Big Difference!


Edited by JohnBear, 01 August 2020 - 04:17 PM.

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#10 Javier1978

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Posted 01 August 2020 - 04:29 PM

I starhop using my 8 dob and 50mm finder from urban skies. M80 is easily seen with that scope and a 25mm eyepiece. Just point to the zone with any finder and look around with a low power eyepiece. M80 will become an easy target for you very soon, just don't waste your time when the moon is so close to it.

Good luck!

Edited by Javier1978, 01 August 2020 - 08:05 PM.

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#11 Alterf

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Posted 01 August 2020 - 06:09 PM

I starhop with a 6" dob at <50x.  That makes it much easier.  In the suburbs, the 50mm finder is a great solution, seconding what others have said.  

 

Also, what are you using as a map?  It takes a while to figure out exactly how what is in the scope corresponds to what you see on the map, especially if the map does not show stars down to the magnitude the scope sees.  Just getting oriented to whatever map you are using takes some time.  Once that is achieved, the job should be much easier.

 

Val



#12 Jon Isaacs

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Posted Today, 05:56 AM

Scott:

 

First:  An 8 inch Dob is good scope for urban deep sky.  An 80mm F/6 is essentially a super finder but only goes so deep. 

 

You have a number of issues going on simultaneously.  

 

- The moon is near full and not far from M80.  This adds to the difficulty.

 

- You have a only a red dot finder.  For star hopping, particularly from a light polluted backyard, I consider the combination of a red dot or Telrad plus a 50 mm RACI finder ideal.  I just can't see enough to star hop meaningfully without a magnifying finder.

 

- A 2 inch wide field "finder" eyepiece is a big help. With your XT-8 plus, something like the 32mm Q-70 would give you 1.9 degrees, the 38mm Q-70 would provide about 2.2 degrees.  The 28mm Deepview provides a field of 1.3 degrees, not bad but the wider fields of the Q-70s make star hopping easier.  

 

- Not sure what to say about the smoothness of your scope.  Tracking and moving the scope should be pretty stable, particularly when using a low power eyepiece for finding M-80.  Generally there is a learning curve and it takes a little while to get it figured out. 

 

With a 50mm RACI finder, star hopping to M-80 should be straight forward, even with the bright moon.  With bright moon and only a red dot and a 1.3 degree field, I probably wouldn't even try.

 

Jon




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