Suggested targets for comparing scopes

[RobertI]

Hi all, 

When my new Skywatcher ED100 finally arrives, I am planning to do a head to head against my Tal 100RS for fun. My expectation from what I have read is that (everything else being equal) the ED100 is likely to discern better low contrast detail in objects such as nebulae and planets, and give a better colour rendition. However performance is likely to be similar on high contrast targets such as doubles of equal brightness and the moon. 

So, during the long wait for delivery, I am putting together an observing list for the comparison. Current list is:

1. Coloured double - Alberio
2. Carbon star - Garnet Star 
3. Challenging double of equal brightness - ?
4. Challenging double of unequal brightness - ?
5. Faint nebula with and without filters - Veil
6. Brighter nebulae with and without filters - M57, M27, M97
7. Galaxies - M81,M82, M32
8. Jupiter and Saturn
9. Open clusters - Caroline’s Rose, Owl cluster
10. Glob clusters - M13, M92

What do you think? Have I missed anything? Any ideas for items 3 and 4? Any other thoughts? Thanks! 

Rob
 

 

[vlaiv]

Moon is probably implied but not on list - maybe add it just so you don't forget about it

Boötes has multiple doubles. Izar being nice example with mag 2.37 / mag 5.12 and 2.8" separation. Then there would be Zeta Boötis, that is going to probably be too much for 4" scopes - 1" separation and mag 4.5/4.6, but you can try to see how each scope is rendering the image (maybe detect elongation?).

Mu Boötis maybe better candidate for same brightness close components. It is actually quadruple system, with primary being some crazy small separation of 0.08" but secondary has much better stats: "The components of μ2 Boötis have apparent magnitudes of +7.2 and +7.8 and are separated by 2.2 arcseconds."

Another example of high contrast very difficult double would be Antares. Main star is variable 0.6-1.6 while secondary is 5.5, separated at 2.45", but very low close to horizon, can it be split?

[Sunshine]

I think Jupiter would pretty much be the test for a low contrast detail, especially comparing two scopes side by side.

[RobertI]

14 minutes ago, vlaiv said:

Moon is probably implied but not on list - maybe add it just so you don't forget about it

Boötes has multiple doubles.

Thanks Vlaiv, you’re right I did miss the moon! Good call about Bootes, my western view is blocked by the house but I may be able to get it. Might even be worth finding a different site as there seem to be a lot to chose from. Thanks for the suggestion. 

 

17 minutes ago, Sunshine said:

 

I think Jupiter would pretty much be the test for a low contrast detail, especially comparing two scopes side by side.

 

Thanks, yes I am planning to spend a good time on Jupiter, might even try some colour filters for fun. That is assuming the scope arrives before Jupiter disappears again! 

[John]

Pi Aquilae is a good challenge for a 100mm - equal mag 6 stars 1.5 arc seconds apart.

Delta Cygni is an uneven brightness pair (mag 3 and mag 6) about 2.7 arc seconds apart.

Mag 13 star next to the Ring Nebula is a good test of 100mm scopes. Central star of M27 (Dumbbell Nebula) is another one.

Bright stars such as Vega, Altair and Deneb to compare CA. Racking through the point of sharp focus a bit either side and watching the airy disk expand is interesting.

Scatter around point sources might be an interesting comparison to make.

Keep the magnification when comparing as close as possible - at least these scopes are of similar focal length.

If the seeing is mediocre that will hamper proper comparison.

I moved from a TAL 100 to an ED100 as it happens, many years back now. Both very good scopes of their type of course

[RobertI]

9 minutes ago, John said:

Pi Aquilae is a good challenge for a 100mm - equal mag 6 stars 1.5 arc seconds apart.

Delta Cygni is an uneven brightness pair (mag 3 and mag 6) about 2.7 arc seconds apart.

Mag 13 star next to the Ring Nebula is a good test of 100mm scopes. Central star of M27 (Dumbbell Nebula) is another one.

Scatter around point sources might be an interesting comparison to make.

Keep the magnification when comparing as close as possible - at least these scopes are of similar focal length.

I moved from a TAL 100 to an ED100 as it happens, many years back now. Both very good scopes of their type of course

Thanks John, they sound very accessible targets from my garden observing site. I’ll also add scatter to the list of things to look for.  I meant to mention that i found a way of getting equal magnifications in both scopes of 50x, 100x and 200x,  partly thanks to the incoming Baader 2.25x barlow (thanks for the recommendation!). I know the different eyepieces in each scope will add some uncertainty to the comparison, but hopefully close enough to not be significant compared to the objective lenses. 

[steveex2003]

Have you compared your two scopes yet? What did you find?

[RobertI]

Still wating for the new scope to arrive!! Will be another two weeks according to the supplier, but I'm not holding my breath. But rest assured I WILL be doing this comparsion!

[steveex2003]

I do enjoy an A/B shootout report.

[Alkaid]

Although it’s a a lunar high contrast target, I would love to know the comparison between these two on Copernicus at high power. Say both at roughly x200 for one test, and also an image breakdown test whereby you keep pushing the power.  You might find that the ED100 will allow much higher powers to be employed, would be fun to see how hard each one can be pushed.

[Astrid]

On 22/07/2020 at 23:59, RobertI said:

Hi all, 

When my new Skywatcher ED100 finally arrives, I am planning to do a head to head against my Tal 100RS for fun. My expectation from what I have read is that (everything else being equal) the ED100 is likely to discern better low contrast detail in objects such as nebulae and planets, and give a better colour rendition. However performance is likely to be similar on high contrast targets such as doubles of equal brightness and the moon. 

So, during the long wait for delivery, I am putting together an observing list for the comparison. Current list is:

1. Coloured double - Alberio
2. Carbon star - Garnet Star 
3. Challenging double of equal brightness - ?
4. Challenging double of unequal brightness - ?
5. Faint nebula with and without filters - Veil
6. Brighter nebulae with and without filters - M57, M27, M97
7. Galaxies - M81,M82, M32
8. Jupiter and Saturn
9. Open clusters - Caroline’s Rose, Owl cluster
10. Glob clusters - M13, M92

What do you think? Have I missed anything? Any ideas for items 3 and 4? Any other thoughts? Thanks! 

Rob
 

 

Hi! That list looks great! 

But may I ask, what filters do you use/will use for nebulae? I heard that the only nebulae visible without a filter is M42 (orion). Is this true?

Thanks in advance!

[RobertI]

2 hours ago, Alkaid said:

Although it’s a a lunar high contrast target, I would love to know the comparison between these two on Copernicus at high power. Say both at roughly x200 for one test, and also an image breakdown test whereby you keep pushing the power.  You might find that the ED100 will allow much higher powers to be employed, would be fun to see how hard each one can be pushed.

Your wish is my command. It's added to the list! It might be a little while before I can manage it, but at least the scope has arrived now!

[RobertI]

2 hours ago, Astrid said:

Hi! That list looks great! 

But may I ask, what filters do you use/will use for nebulae? I heard that the only nebulae visible without a filter is M42 (orion). Is this true?

Thanks in advance!

Thanks! Apart from the Orion Neb, there are plenty of other nebulae visible without filters including the Lagoon, The Swan , the Trifid, The Ring, the Dumbell and the Crab Neb.

Most of these brighter nebulae will show up better with a OIII or UHC filter, and there are a host of fainter nebulae which are only really visible with one of these filters.

So I'll be using one of these two filters.  

[Alkaid]

Having owned a TAL100RS myself previously, I’m going to be reading this thread with huge interest, what a great comparison of Achromat vs Apo. Can’t wait!

[jetstream]

On 22/07/2020 at 15:59, RobertI said:

Have I missed anything?

How about this- Put Alnitak on the edge of the field and view the Flame nebula no filter- this is a good test of everything.

One more: go up and over from there and easily view M78- scan from there looking for the edge of Barnards Loop- your 100ED will show it for sure under dark skies, you need a 40mm or lower fl EP IMHO.

Edited September 13, 2020 by jetstream

[jetstream]

On 12/09/2020 at 15:19, Astrid said:

I heard that the only nebulae visible without a filter is M42 (orion). Is this true?

I mentioned this to encourage an easy to spot nebula with no filter but there are piles of them visible.

[RobertI]

50 minutes ago, jetstream said:

How about this- Put Alnitak on the edge of the field and view the Flame nebula no filter- this is a good test of everything.

One more: go up and over from there and easily view M78- scan from there looking for the edge of Barnards Loop- your 100ED will show it for sure under dark skies, you need a 40mm or lower fl EP IMHO.

Two nice suggestions there to include over the winter, thanks. These are of particular interest to me as I have never seen the flame or Barnard’s loop. I also have a nice 2” 38mm EP which works in both scopes, but sadly much smaller FOV in the Tal. Looking forward to trying  👍

[SiriusB]

Here's one for the list i made earlier, Blue Peter style.

https://stargazerslounge.com/topic/359653-a-double-star-challenge-epsilon-lyrae/

TBH Rob, the best targets for comparison are those which interest you most.

If you live & breathe planetary, there's your comparison objects. If you rarely look at doubles, it's pretty academic which scope's better for those.

.....Though i suppose most of us like a finger in most of the celestial pies. 😉

So your rounded list is a good idea.