Re: (meteorobs) Telescope for meteror bserving
Bottom line: your telescope sounds like it is suitable to observe
> I have a 6" f.5 refractor with a wide angle Erfle 65deg. WFV giving over
> 3deg. on the sky.
I use a 5" f/5 refractor with a wide angle Koenig 65deg, but in a 1.25"
tube the field diameter is 52 degrees apparent, 2.6 degrees true field.
The narrow field improves my plotting accuracy, but I see fewer meteors
than with the wider field. Given that I still see about 12 per hour on
average, it's a trade I am happy to make. The star images are also
crisp to the field's edge.
> The aperture in centimeters times 1.4 is over 21.
> This exceeds the NAMN limit of 20 by a small amount.
This is a guideline but governed by the diameter of the eye's pupil.
Your refractor's aperture is 152mm. 21 times magnification
gives an exit pupil of 7.2mm. Now if your eye's pupil extends a mm
or two larger you can accept the beam. The canonical diameter for
young people is 8mm but normally reduces with age.
I have used a 7.1mm exit pupil, as commonly found with astronomical
binoculars like 7x50, 11x80 foir telescopic-meteor watching. My
experience was that the bright field reduces the numbers of faint
meteors seen, because of reduced contrast. This was most evident during
the (northern) summer meteor season. The brighter field was more tiring
too. The larger exit pupils give you less scope to move your head
slightly without losing any of the beam. Hence I recommend a slightly
higher magnification. The canonical figure in imperial units is 4x per
inch of aperture. For instance I use a 32-mm focal length eyepiece.
Individuals vary and you have to find a setup which you are comfortable.
If you like the 21x then stick with it.
> I am wondering if
> this telescope would be useful for observing meteors despite this
> discrepancy in criteria.
Yes it would. You'll need a star diagonal to place the eyepiece in a
comfortable location, and an eye-patch so that you can have both eyes
open, but only one viewing. Comfort is critical so either or both your
chair or telescope mount must be adjustable in height. I use an armless
computer chair and the telescope is tripod mounted.
Since the instruments match well, I could send you some of the IMO
`D' charts I use.
> Though I am not yet experienced enough in
> visual observing, I was thinking of possibly preparing this scope so
> that I can use it when I feel competent enough. Though it has a
You'd certainly be welcome. There are only a few of us telescopic
observers scattered around the world, and it's hard to get statistical
meaningful results with so few meteors recorded in comparison to visual
> mounting that can be polar without a drive, I usually swing the polar
> axis down to use it as an az-el mount. This avoids the gimbal lock near
> the pole, and at this low power it doesn't need a drive in normal visual
A drive isn't necessary, but convenient if you have one. I roughly
align my German mount with the celestial pole so I only have to tweak
in one axis.
While on this topic, has anyone had experience of the Orion 80-mm and
125-mm angled binocular telescopes?
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