Observing with small scopes on farmers field on way to Rosliston

11.20pm Saturday 9th June  – 1.50am Sunday 10th June 2018

Damian and I have just returned from a great observing session lasting a good two hours in a quite dark farmers field / public footpath, on the way to Rosliston from Lichfield…

Using only small scopes- Sky Watcher Equinox Pro 80mm and a 77mm triplet fluorite spotting scope, we scooped a range of objects including Jupiter and the Great Red Spot, Dumbbell Nebula, Ring Nebula, M3, M56, Harvard 20, M71, M51 and repeated definite direct vision observations of M101 amongst others……and all this on a night predicted to be quite poor for observing.

I also saw three meteors and what must have been my first ever sighting of an Iridium Flare – wow! I saw the flash of the flare and then looked at Heavens Above website and realised that one had been predicted to occur in that part of the sky at that time.

Just goes to show- you never can tell what a night will be like! I notice that in another post on viewing tonight, Nick has commented how clear the sky became.

The spotting scope put up quite a good show and really demonstrated its great portability. Needs some thought ‘re adding a finder and counter-balance weights though.

We noted the following differences and similarities between the design of the apo-chromatic spotting scope (SS) vs. dedicated app-chromatic astronomy scope (SW) of similar aperture and focal length:

1. The view in the SW was more contrasty with blacker background than in the SS. As a result, objects appeared brighter at similar magnifications in the SW. this may be due to the need for extra optics in the SS to correct the view for daytime viewing so that it is upright and correct way around. In spite of this difference, it did not significantly affect the amount of detail that could be seen in the SS compared to the SW.

2. Both showed similar small amounts residual chromatic aberration on edges of Jupiter, although SW possibly slightly worse.

3. The views were nevertheless comparable at similar magnifications – any differences were really a matter of personal preference and would not cause us to buy one over the other.

4. The manufacturer-specific eyepiece fitting used in the SS means that standard astronomical eyepieces can not be used. This limits the magnification to maximum 60x because that is the highest magnification eyepiece available for the telescope. At 60x both scopes showed a similar level of detail on Jupiter’s disc and the Great Red Spot was just visible. However I was able to increase the magnification in the SW to x125 by changing eyepieces and a wealth of detail on Jupiter’s disc became visible and the Great Red Spot became large and obvious. The benefit of magnification on a planetary disc was less useful for deep sky objects where the limited aperture meant that the object would become diffuse and become difficult to focus at higher magnifications suggesting that for most astronomical observations the 60x magnification limit on the SS is probably sufficient.

5. The 45 degree diagonal on the SS was not as useful as the 90 degree one on the SW for night time viewing, especially when looking at objects near the zenith or when trying to find things in the sky. The scope definitely needs an extra finder shoe attached to it in some way to facilitate the use of a finder.

6. The SS had a small inbuilt dew shield which was insufficient at night. It needs a bigger one made – an easy task.

7. The SS is incredibly portable without all the paraphernalia that went with the SW and this makes it as excellent choice to take on holiday or as the ultimate grab and go scope.

8. The excellent light weight tripod that comes with the SS is good but had its limitations. My heavy duty Mandrotto tripod and mount on my SW out-performed the smaller Manfrotto one with the SS but those can be changed and this simply the limitation of the physics – light weight tripods and heads are limited in what they can do. I was actually very impressed with how stable the tripod was with the SS on it. A bigger issue is balance – the SS was not properly balanced and needs some counter balance mechanism for night time viewing where it is going to be pointed upwards rather than horizontally as occurs during its intended daytime use.

Andy

A few additional notes from Damian:

Both instruments showed varying amounts of field curvature towards the outer 15-20% of their FOV.

The SS showed a whiter Jovian disc whereas the SW had a more creamy appearance – nothing wrong with either, some would say the whiteness was more ‘clinical’, others would say the creaminess offered a more pleasing and natural view. Could be from the objective or the eyepieces used.

The 20-60x zoom used with the SS was not as good as the Baader on the SW. Checking reviews of the unit online highlighted it’s shortcomings (“a narrow FOV at 20x” – like looking down a straw – makes me realise just how accustomed Andy and I have become to fantastic 100 degree views – and “pretty useless above 40x”). The 32x eyepiece also available was a “much better corrected optic” – wider and ‘cleaner’, although still showed some field curvature and chromatic aberration at the extremes of the FOV.

Jupiter on axis though through the SS was very sharp at 60x with four bands visible and the GRS clearly defined. Could not see the ‘streamer’ that Nick mentioned though in his post (but he was using 6” of aperture and over 200x mag!)

The Background sky displayed in the SS was not as black and the view not as contrasty (using the zoom, should have tested the 32x eyepiece) and this was rather disappointing considering the make of the SS and it’s fluorite Lens (which refractor nuts on the Astro forums go nuts over!)

I also now wonder just how quickly the objective had started to fog up into the evening… did this effect the contrast..? I suspect yes to a small degree but I think, having ready many reviews online with regards to using a SS for Astro uses, that even the best SS’s from the ‘big brands’ have until recently not been up to the quality of telescopes. Many times it was mentioned that for a long time astronomical telescopes have undergone the dreaded high power star test whereas SS objectives are rarely scrutinised in such ways… but again, it could be the eyepiece units used on SS are not up to the quality of astronomical units…?

The SS also had a very limited depth of field and I found it quite difficult to nail focus.

The 45 degree angled eyepiece was comfortable… up to a point, then it became a pain to have to raise a tripod leg to reach higher areas without breaking your neck.

Star hopping was great – the views matching directly to Sky Safari (of course you can switch them around as needed), which also meant that your manipulation of the scope was intuitive. This made it easy to locate faint objects – M101 for example (a notoriously dim object).

Other limitations are the lack of using filters.

Advantages are it’s extreme portability (one trip from the car up the track – carrying the SS in it’s case over the shoulder with a chair in one hand, eyepiece in a pocket, food and drink in a bag carried in the other hand with a tripod under that arm, ruggedness – manufacturer quoted as ‘shockproof’, waterproof to 3 metres, use of a travel tripod – the unit that Andy used for a similar sized telescope would have taken your entire luggage allowance! A lighter unit for the SkyWatcher would have made it very wobbly and negated much of it’s high power views.

Damian

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