Observing Report: July 17, 2015

Posted in Observation Record on July 17, 2015 – 10:33 PM
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The skies were clear and I’ve had an itch to visually observe for a while. I got out to my club’s observing session last Friday night, but spent most of the evening helping others, so didn’t get to do much of my own work. I’m fine with that as I really enjoy helping others (especially with kids) how to use their telescope and showing them some of the things that are out there. I am growing increasingly frustrated with my driveway astronomy though – too many trees and too much light. I feel like I try to observe the same targets, but at least I reinforce the placement of constellations and stars… one of these days I’ll learn for good!

Location: Home, Raleigh NC
Telescope: 10″ Dob
Seeing: Good
Other: Poor transparency. Lots of faint clouds. High humidity (some dew, but not bad).

M13: I started the night on M13, the Great globular cluster in Hercules. Easily found in my Explore Scientific 24mm, a ball of stars with noted with a few points of light. However, upon moving up to my 8.8mm, 82 FOV (136X, 0.60 degrees in the eyepiece) many individual stars were noted. Stars had a bluish hue and were tightly packed into a grey mass in the middle with hundreds of distinct stars observable.

NGC 6207: I will need to go back and check my notes about previous observations of this object, but this was a challenging object. I was only able to see it for fleeting seconds with averted vision. Yet, when it did pop into view it seemed somewhat large. At times I felt it was almost circular (a little elongated) and other times I saw more of a crescent shape.

NGC 6229: Continuing on in Hercules, but moving up into the head area is NGC 6229. This was difficult to transpose from the sky atlas to the stars, perhaps because it is reasonably close to the pole. The bright core was obvious, though at no magnification (up to 136X were many stars resolved. The sky was getting hazy which was not aiding in my observation. Howver, this beauty is flanked by two stars of nearly even brightness. Further followup showed them to be 8th magnitude while the cluster is listed at magnitude 9.40.

NGC 6426, IC 4665, 61 Oph: I had a brief window where parts of Ophiuchus were visible between the break in trees where my driveway cuts through. I tried my best to find NGC 6425, but it didn’t happen. There is a spot I think I saw it, but couldn’t confirm. It shouldn’t be hard to find as 61 Oph is a very nice double star nearby (6th magnitude, nearly white, and easily split at 85X). The cluster is listed as magnitude 11.20, but pretty small. Perhaps another day. However, while in the neighborhood I pushed my scope up, just above Beta Oph and came to IC 4665. Open clusters can be a bit boring, but this was a very nice cluster with about 20-30 bright stars (7-8th magnitude) and many more dimmer stars.

I packed it in after about a hour. The humidity and street lights started to get to me and I didn’t have a good observing plan. One day I’ll stick to my idea of using my driveway for stellar observations (double stars)… or I’ll bring out my tracking mounts…

Explore Scientific 24mm 82 degree Eyepiece

Posted in Hardware on July 9, 2015 – 5:56 PM
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Up until this week, my collection of eyepieces was mostly ones I got either with a telescope or through the Celestron beginner’s accessory kit which provided 5 plossl eyepieces and a barlow. I’ve picked up a few others along the way, particularly a couple TMB Planetary eyepieces, a couple inexpensive 2″ eyepieces, and an Orion Expanse 20mm which quickly became my go-to eyepiece for most things. For some reason over the past few months I’ve had the hankering to put together a set of nicer eyepieces at a reasonable cost – all my research led me to the explore scientific line.

Enjoying the view from the Orion Expanse was the key for me. While Plossl’s typically have a 50 degree field of view, the Expanse comes in at 66 degrees. So what would an 82 degree eyepiece do? And yes, 100 degrees (and even 120 degree) eyepieces are out there, but beyond what I’m willing to spend. But how does the FOV increase and keep magnification the same?

I decided to compare the Explore Scientific 2″ 24mm 82 degree eyepiece to a 25mm Celestron plossl. The comparison was done on my 10″ dob (fl 1200mm, f/ 4.7). I felt the ring nebula was a good target to compare magnification, image clarity, and color.

The Explore Scientific eyepiece is a pretty big and pretty heavy eyepiece coming in at about a pound and a half. I was also a little disappointed because fully seated in my stock focuser there was not enough travel to allow it to come to focus. I had to pull it out a bit and tighten down the screw which allowed it to focus. However, once in focus the view did not disappoint. Now at 50X magnification and an apparent field of 1.64 degrees I could still see M57 clear and the hole in the middle was evident. There was a slight bluish hue and crisp stars most of the way across the field of view which certainly looked large.

Switching over to the 25mm Plossl (48X, just over 1 degree apparent FOV) I immediately got my answers.
1. The wider field of view really does not impact the magnification. The plossl looked just about as good on the ring nebula, but the starfield is limited and the edge of the field now looks like you are looking down a long tube. Same magnification, but wider field viewed in the eyepiece.
2. The explore scientific had a crisper image at the edge of the field with only minor aberrations as you moved toward the edge of the field. The plossl wasn’t bad, but even with the narrower FOV, some lengthening of the point of light was noticable.
3. The color transmission was a bit better in the explore scientific, particularly looking at star colors, but the difference seemed reasonably small (perhaps under better skies it would look different).

Overall, I was impressed with the Explore Scientific 82 degree eyepiece – it performed as I hoped. There was good contrast, a very clean image, and the wide field makes viewing more enjoyable – and keeps the object in my eyepiece for longer. However, I was also impressed with the plossl I had been using for years. Sure, it doesn’t have the field of view, but considering cost, the view did not disappoint. It goes to show that you get what you pay for, but the inexpensive ame brand lenses offer great value.

Perhaps one day I will compare this eyepiece to a Nagler, Ethos, or similar – an eyepiece generally considered as superior… and will update this review.

Observing Report: May 13, 2015

Posted in Observation Record on May 14, 2015 – 5:35 PM
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Once again, it had been a very long time since I got out with the telescope. A very cold winter followed by a cloudy Spring has left me needing photons. I needed a fix so bad, that I took an hour or two on Wednesday night, where it wasn’t even dark enough to see stars until almost 9pm, to pull the scope out.

My skies are quite light polluted. I bought an iPhone app which measures sky brightness and got a reading of 4.99 NELM (there was no moon interference). I’d say that is pretty accurate. I had decided to work on double stars / star clusters, but it had been so long the lure of the Messier DSO’s were calling me to me.

Location: My Home, Raleigh NC
Telescope: 10″ Dobsonian Reflector
Seeing: Fair

M51: My yard has many tall trees around. From my driveway, the Big Dipper loomed large overhead. I was able to very quickly local M51. This object is one I struggle with sometimes, especially in light polluted skies. But I found it on the first try. Two cores could easily be seen, but little other structure.

M63: I moved over to Canes Ventici and found M63. This was an interesting object which came into and out of view. Averted vision was required. No structure could be seen, but the galaxy was clearly anchored by a star on one side. I had some width, but clearly more elongated. I found it best with my trusty 20mm eyepiece (60X). I explored different magnification and filters to try and tease out some more detail. At lower magnification the sky brightness dimmed the object and when I tried to increase the magnification with my 9mm eyepiece, the sky was dark, but the galaxy lost its contrast. Wide field (2″ eyepiece, 35mm) with a skyglow filter completely lost the galaxy. Adding a Ultrablock LPR filter to the 20mm eyepiece also reduced the contrast of the galaxy versus the skyglow.

M94: Also in Canes Ventici I found M94. This object was bright, compact, and nearly perfectly round. At first, I thought it was a globular cluster, but at high magnification was unable to resolve into pinpoint stars.

M109: Moving back to the Big Dipper I looked for M109. This object was a challenge, but I was finally able to make out the faint fuzzball. There was not much to see at any magnification. Another inspection should be repeated under darker skies.

M3: I couldn’t end the evening without getting one globular sighting. M3 was high in the sky and always one of the best globs in the sky. At 133X many jewels sparked in the eyepiece. Globular clusters are always sights to behold.

Saturn: Luckily for me, as I prepared to pack up I saw a yellowish star just over the trees. Having a strong suspicion, I turned my telescope towards it and sure enough saw the familiar rings. Saturn is back in the evening sky! The rings were open nicely, though clearly different from the last time I viewed it – probably last summer. I pushed the magnification up to 200X with my 6mm TMB planetary eyepiece and I could make out a little bit of fleeting color variation on the disk. It was reasonably low on the horizon further compounding the marginal seeing conditions.

It was a great night. Warm and clear. Very comfortable other than a few mosquitos. I’m definitely craving some new eyepieces and got envy when I saw a fellow club member’s Moonlite focuser for his Dob. Hopefully more clear nights are upon us!