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query on Orion

Started by BABOafrica, 02/27/2011 06:33AM
Posted 02/27/2011 06:33AM Opening Post
I looked thru my new home made 10" Dob last night to look at the Orion constellation last night. I was particularly interested in looking at M42. At least I think that is what I was looking at.

It was must first time looking at a nebula. I watched it intently for a fairly long time -- a full 20 minutes non stop. My eyes were nicely dark adapted.

There was not a cloud anywhere in the sky. I sure I was looking at something in the Orion constellation. And the night air was perfectly still -- perfectly.

I was surprised to see how ghostly it looked. I could not make out any edges. Is this normal?

I was using a 8mm eyepiece, which admittedly is not exactly a quality EP. Would that be the reason?

Another factor worth mentioning. I could not get to a dark site. I was viewing from a place not far from the city (Nairobi) and there was significant light pollution (no Milky Way visible).


In lumine tuo videbimus lumen.

8O Home-made 10” Dob / Home-made 4” refractor

EPs: Konig 32mm (1.25") / Zhumell WF 30mm (2") / Nagler 13mm T1 / Orion Sirius Plossls 25 & 10mm / Zhumell Plossl 9 mm / Meade MA 9mm
Posted 02/27/2011 06:44AM #1
That sounds like the Orion Nebula from a light polluted place.

A nebula, by definition, has no really well defined edges. It is a gas "cloud."

You may be mislead by photographs of the nebula, but you have to remember that photos are highly processed to bring out contrast (edges among other things).

Posted 02/27/2011 10:13AM | Edited 02/27/2011 10:23AM #2
Joseph Babendreier said:I was particularly interested in looking at M42. At least I think that is what I was looking at...It was must first time looking at a nebula...I was surprised to see how ghostly it looked. I could not make out any edges. Is this normal?
Joe: Your predicament is common for first-time viewers. At public star parties I display two photos of M42, one taken by the Hubble Space Telescope that everyone has seen and expects to see through my telescope's eyepiece, and the other representing what is actually visible. I will attach the second one of these two photos to this posting to illustrate; it obviously is nothing like any of the M42 images taken by skillful astro-imagers and laboriously processed to bring out details and red-green-yellow coloration that no-one has ever seen either with the naked eye or through a telescope.

Attached Image:

Herbert Kraus's attachment for post 140015

NexStar 8i SCT, Orion 80ED APO refractor, Orion 120 mm EQ refractor, 3.5-inch Questar
Posted 02/27/2011 11:28AM | Edited 02/27/2011 02:42PM #3
Hi Joe, the other responders are correct. And even the illustrative pic provided by Herbert displays much too much contrast & brightness for the location you had (it is also a lower-power & wider-field view than you had). Observing Tips: Dark-Adapting your eyes by not looking at any bright lights for 20-30 minutes & longer helps with seeing dim faint light thru the scope, as well as looking towards the side of or slightly beyond a faint object (known as Averting your vision) vs straight-on towards its' center. Draping a dark cloth over your head & the focuser helps keep stray city lights out of your view, too, as well as preserves dark-adapted night vision. (like the old-time photographers with their glass plates & tripods).
Posted 02/27/2011 06:24PM | Edited 02/27/2011 06:40PM #4

I think another issue here may be the smallish field of view your 8mm eyepiece is giving you.

I now see the focal length of your 10" dob is 44" or 1118mm, so the 8mm eyepiece is giving you 140x magnification. I'm purely guessing that your eyepiece may have an apparent field of view around 50 degrees. OK, if so, that means the true field of view you're seeing is about 1/3 of a degree.

You may get a better view of the nebula by using an eyepiece that gives a larger true field of view. I see in an earlier post you have a 12mm eyepiece, try that one it may work better. If you have a chance to find an eyepiece of 20 to 26mm, that would give more like one full degree.

Just a suggestion. Best of luck!