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Something I didn't expect....

Started by markvcostello3, 02/28/2011 02:18PM
Posted 02/28/2011 02:18PM | Edited 03/01/2011 02:06PM Opening Post
I was out last Saturday with my relatively new 5" achromatic refractor (achro), an Explore Scientific AR127. I took advantage of the moon rising late to observe and draw some deep sky objects. One of them was M35. I also went looking for nearby NGC 2158. I couldn't quite see it at 26X (Celestron Ultima 31mm) or 103X (Baader Hyperion 8mm). So noting that this complex was in nearly the best position it could be (close to zenith) and really wanting to see if I could see NGC2158, I went for 206X (inserting a TV barlows lens). Much to my surprise, it worked. I was able to see a grainy haze with individual stars winking in and out. I also tried this on Cluster NGC 2420 and found that the view was better at 206X than 103X. Ditto with NGC 2392 (the Eskimo Nebula).

I've had this experience before with M11 the Wild Duck Cluster. The question I have for y'all is this: From way back in the late 60s reading Edmund catalogs, I had always thought that deep sky objects (DSOs) should be viewed at low to mid power. Yet for a few of them, it appears that high power seems to work even to the point of making them "brighter." Is this correct, or should I stick to low or medium power for some DSOs.

Thanks for your response....


Mark Costello
Matthews, NC

Mark Costello
Matthews, NC, USA

"I hear you're mechanically inclined. Did you ever do anything with perpetual motion?"

"Yeah, I nearly had it a couple of times."
Posted 02/28/2011 02:28PM #1
Mark,
You will find that some DSO's, especially planetary nebs and small globular clusters really need higher powers to properly view them. You are correct when you say they get brighter.
I always experiment with my magnification on new objects, sometimes it will surprise you.
Clear skies,
Brad

Posted 02/28/2011 03:18PM | Edited 02/28/2011 03:19PM #2
I've had this experience before with M11 the Wild Duck Cluster. The question I have for y'all is this: From way back in the late 60s reading Edmund catalogs, I had always thought that deep sky objects (DSOs) should be viewed at low to mid power. Yet for a few of them, it appears that high power seems to work even to the point of making them "brighter." Is this correct, or should I stick to low or medium power for some DSOs.

Mark:

You pretty much answered your own question... Let what you see at the eyepiece guide you. I think you found your a new trick, something you will try in the future on other objects.

One reason why I think it is important to have several eyepieces spaced carefully is that it gives you the chance to play around and determine which view shows you the most, which one you prefer.

Your eyepieces are like the gears on your bicycle, you want to make your choices based on some theory and experience but in reality, you just let your legs figure out the right gear...

jon
Posted 02/28/2011 04:26PM #3
I agree that many deep sky objects get better at different, including higher magnifications.

But, curiously, I do not beleive they get "brighter" at least in the photometric sense of the term. What is happening is that at higher magnifications, all brightness levels decrease. But they decrease faster in the shadows and other dark levels than they do in the brighter areas. As a result, there is greater contrast. They eye is not very good at determining absolute brightness levels, but very good at determining difference in brightness levels. Many dim objects sometime rise above the background better when viewed at higher power.

Alex
Posted 03/01/2011 03:14PM #4
Mark Costello III said:

I was out last Saturday with my relatively new 5" achromatic refractor (achro), an Explore Scientific AR127. I took advantage of the moon rising late to observe and draw some deep sky objects. One of them was M35. I also went looking for nearby NGC 2158. I couldn't quite see it at 26X (Celestron Ultima 31mm) or 103X (Baader Hyperion 8mm). So noting that this complex was in nearly the best position it could be (close to zenith) and really wanting to see if I could see NGC2158, I went for 206X (inserting a TV barlows lens). Much to my surprise, it worked. I was able to see a grainy haze with individual stars winking in and out. I also tried this on Cluster NGC 2420 and found that the view was better at 206X than 103X. Ditto with NGC 2392 (the Eskimo Nebula).

I've had this experience before with M11 the Wild Duck Cluster. The question I have for y'all is this: From way back in the late 60s reading Edmund catalogs, I had always thought that deep sky objects (DSOs) should be viewed at low to mid power. Yet for a few of them, it appears that high power seems to work even to the point of making them "brighter." Is this correct, or should I stick to low or medium power for some DSOs.

Thanks for your response....


Mark Costello
Matthews, NC

Edmunds' advice was wrong then and wrong now. How much power you need to use depends on the object. It is my observation that most amateurs use too little rather than too much magnification on the deep sky.

Uncle Rod

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Posted 03/08/2011 04:37AM #5
Mark,
I had a similar experience last night when I was looking at M108, M109, and the Owl Nebula. I sometimes use a very low power 30x eyepiece to get my bearings when I star hop. Last night the two galaxies were barely noticeable because of ambient light pollution. Bumping up to a 50x made them noticeable. Going to 115x made them obvious and gave them a rough shape. Doing the same thing with the Owl Nebula had an even greater effect and I found it looked even better at 187x than at 115x.

Getting my eyes dark adapted does more than anything though. Oftentimes I don't allow enough time to dark adapt to really get good deep sky viewing. Looking for dim objects in the first 30 minutes will just frustrate me. Sticking it out past that point makes it worthwhile and rewarding. I also found the skies to be much clearer and darker after midnight in my semi-rural neighborhood which is not that far from some larger towns. Once a lot of people have gone to bed the ambient light is greatly reduced. The old adage that the best things comes to those who wait holds true when stargazing. This is definitely not a hobby for people seeking instant gratification!
Regards, Kevin Krepps