Eyepieces

[Dave3216]

Hey guys, my son and I need help. We recently purchased a Skywatcher classic 150P dobson telescope. We are new to Astronomy and had a few questions about the eyepieces. We used the 10mm that came with the telescope, to view Jupiter, it was fantastic, we then used same 10mm to view Saturn, although it was clear and we could see the rings, there was 4 ghost images of saturn around the actual planet, can someone tell me why this happened?

I also did some research on viewing solar system planets, i came to the conclusion that for best results a 6mm eyepiece would be best, is this correct? and should i use a wide angle eyepiece or just the normal one?

Lastly what should i use to view nebula? We have tried looking at some using Stellarium as a guide, but have found nothing so far, probably something i haven't done right.

Thanks in advance. :thanx:

[Stonius]

Nebulae can be faint, especially if viewing from light polluted skies. The trick with observing deep sky objects is about training yourself to discern the slightest glimmer of light. They won't look like long exposure photographs.

The reflections are possibly a result of the eyepieces not being coated? Not sure. Certainly sounds like internal reflections of some kind. Do you get the same with the other EP?

Best,

Markus

[AndyG]

G'day Dave,
I'll leave the EP questions to someone more enlightened/experienced, but perhaps I can share an idea on the above from a similar "beginners" POV as myself.


I suggest you install a copy of SkySafari for your phone/tablet etc. Go to [Search] > [Deep Sky Objects], and "sort by visual magnitude". SkySafari should grey out objects that are not visible from your location. You should find "NGC 3372 - Eta Carinae Nebula" as an item towards the top. This is going to be amongst the brightest and largest things you'll see visually (Easy mode).



Once you can see this, you'll get an idea about what is realistic in your situation. Things like scope aperture, your eyes' health and dark adaption, ambient light (light pollution, etc), and air cleanliness/weather etc, will all play on what you can percieve. Start with the example above, then work down the list of fainter objects.



As you work down the list, you may attempt to identify the challenges working against you (listed above), and do what you can about them to get a better result. Consider: https://en.wikipedia.org/wiki/Averted_vision



All the best :)
Andy.

[m11]

Hi Dave,

To eliminate the issues regarding the eyepieces, do you have another eyepiece to test to see if you get the same reflections? Usually there is a lower magnification eyepiece to test with?

Was the moon or a similar light source close to Saturn at the time that may have contributed to the issue?

In terms of eyepieces, it is really subjective as people have different needs and criteria they use to determine what is best. There are some eyepieces geared for planetary like orthoscopic eyepieces but even basic eyepieces will show detail with a scope. Generally many people start with plossls and collect eyepieces as they go along.

Nebula is very dependant on light pollution and light conditions. Dark skies help due to the contrast and little light pollution.

All the best. :hi:

M11

[Dave3216]

Thanks for the reply Markus, when i used the 25mm wide angle i also got the reflection, but not when looking at Jupiter, just Saturn. But as some one said before the moon was close by and very bright that night.

[Dave3216]

Hi M11, thanks for the reply, yes the moon was very bright and close this night, so im assuming that was the cause?

[Dave3216]

Thanks Andy, i will give it a try this weekend.

[m11]

Hi Dave,

The easy way is to test again with no moon nearby or up?

Give us a yell on how you go. :thumbsup:

M11

[Startrek]

In regard to Saturn having some kind of ghosting view in the eye piece, what time last night were you observing ?

At 8.00pm last night Jupiter was around 65deg in Alt which is an ideal position to view where Saturn was only at 22 deg Alt which is a poor position to view.

At 22deg Alt and lower, objects in the sky ( especially planets ) may possibly cause some kind of optical aberration in the eye piece caused by many factors including the moons glare ( the moon didn’t rise in the east until 11.00 pm last night so it was quite a distance from Saturn.

Ghosting in the eye piece is generally attributed to a very small amount stray light reflecting inside the internal housing.Eye pieces on the lower end of the market with poor anti reflective coatings may cause internal reflections and ghosting

My 2 cents !

[Wavytone]

The one thing that definitely ISNT coated is the Mk I eyeball. Quite possibly there’s a reflection from your eye to the eye lens of the eyepiece and back into your eye.

What can make it worse is contamination on the eyelens (grease etc).

[Dave3216]

It was Fri night, if i remember, moon was bright and Saturn was close by, just above the moon.

[Startrek]

I just checked Stellarium last Friday night and the Moon and Saturn did rise close together.

Did you observe Saturn low in the east or fairly high up in the north / north east ?

I’m tending to think your ghosting is partially the glare off the moon and budget Plössl type eye pieces which most new telescopes come with.

As long as your telescope is correctly collimated , the eye pieces are clean, and you are observing at a decent altitude ( > 45deg ) then I can only suggest it was the moon’s glare together with the budget type eye pieces that caused the ghosting.

The next clear night observe Saturn nice and high and see if the ghosting is still apparent. The moon’s glare / influence over the next week or so progressively diminishes as it phases towards new moon on the 14th June

You have a great starter scope there !

Clear skies enjoy this great hobby

[Dave3216]

It was low east when my son found it, Martin.

[Startrek]

Thanks for the reply, it’s making more sense now about your ghosting of Saturn’s view and the possible reasons behind it

1/ Moon glare

2/ Low altitude ( long angular projection through the atmosphere with air pollution , heat convection causing turbulence etc )

3/ Budget type eye pieces with subjective internal reflective coatings

As mentioned before try observing Saturn at high altitude with no moon around and I’m sure it will be clearer

Based on your 150P dob ( focal length 1200mm )
Your 25mm eye piece will provide 48x magnification
Your 10mm eye piece will provide 120x magnification

With good seeing conditions overhead you could potentially observe the planets and the moon up to 200x magnification ( 6mm eye piece ) with your telescope, however with high magnification you loose clarity and detail so your 10mm eye piece is ideal for planetary and lunar observation at this early stage of your astronomical journey.

Good luck !

[Dave3216]

Thank you.

[Dave3216]

Thanks for your help.

[AEAJR]

Do you know the model/brand of the eyepiece that was ghosting?

I sometimes get ghosting when viewing the Moon with my less expensive binoculars. this is due to internal reflections. But have never experienced that with Saturn.

The ghosting you saw may have actually been the moon throwing stray light in from the side of the eyepiece. I know I have had ghosts in my view which went away if I covered my head/eyepiece with a hood, or shielded it from the side where there was a ground light.

Just some thoughts that might help.