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28
Nov

Telescope buying?! Wonderful!

This can get really complex, and, as you imagined, very expensive.  There is this sudden realization that good scopes are pricey, and the less expensive ones are, well, to be honest, not worth the cash. They end up in closets or basements.  For a first time telescope, especially for kids, I always recommend a really good pair of 8×50 or 10×60 binoculars. These get good use at night, AND during the day… bird, scenic views and the like.  If we are talking seriously into astronomy and telescope are the only choice, then go for the most scope you can afford: one with a quality heavy mount and large aperture.  My close friend Ed Ting has made a wonderful page with a load of buying tips here:  http://scopereviews.com/begin.html Do start there and work through it.  At all costs avoid the department store telescopes. They are a plague in our science with their cheap, shaky mounts and promises of ridiculously high powers 😉

Coupled with a telescope purchase is the inevitable need for some accessories. I’ll list a few here to consider:

  • A wide range of good eyepieces. These get expensive but will last a very long time. I recommend three to start, one for low, medium and high magnification. Magnification can be found by dividing the telescope’s focal length by the focal length of the eyepiece. Typical low power magnifications are on the order of 25-30x.  Medium: 75-150x. High: 200-300x. One rarely uses the high magnification. Honest!
  • A good sky atlas. Good ones can be used for eyes, binoculars and small telescopes like these options: Sky & Telescope’s Pocket Sky Atlas – Jumbo Edition and the Sky & Telescope’s Pocket Sky Atlas.
  • A red-light flashlight. A simple regular flashlight with red cellophane covering is good.
  • Maybe even a subscription to Sky & Telescope Magazine or Astronomy Magazine. These help the newcomer by projecting what good targets will be available in future months.

Stay well and enjoy clear skies!

25
Nov

Jupiter and Saturn’s Big Month Together: 2020 December

Those looking up at the sky through late November to late December are in for a real treat, a close conjunction of Jupiter and Saturn. This is quite an event! It will be easily visible to those with or without optical aid. It takes place early in the evening, so even those who go to bed early can enjoy. All you need is a clear early evening and a low horizon to the southwest. Here’s a short video to show you more. Enjoy! https://youtu.be/rKwFqnVdKiM

 

18
Oct

NGC 6888:The Crescent Nebula

Last night’s target now processed… stage 1…. the initial offering. Sometimes I remain happy with the first edit, sometimes not. This is NGC6888, the Crescent Nebula in Cygnus. The central star is known as a Wolf-Rayet star, WF 136, which is massive and rapidly shedding its outer laters into the surrounding interstellar medium. This whole system is about 5000 light-years distant and about 25 light years across. This image was taken with our 0.7m telescope through several filters: Luminance is a combination of one hour of clear plus one hour of Ha. The color data was taken using Ha, SII, and OIII narrowband filters.

NGC 6888

 

NGC 6888
This edit with a more refined Hubble Color Palette and more extensive stretching to bring out fainter details.

25
Jul

The July Comet C/2020 F3 NEOWISE: Quite a Show!

Comet C/2020 F3 NEOWISE was definitely the comet of the year, one of the best in a couple of decades. Hovering low in the morning sky before dawn, then, later in July making its evening appearance low in the northwest sky after sunset, it provided hauntingly beautiful views of the night sky. Not much impresses more than a comet with a visible tail.

By July 20th, the comet was easily seen without optical aid, about 25 degrees above the northwest horizon just after sunset when the stars started to come out. It sported a long dust tail: to my eyes it appeared some 5 degrees long, but others were calling for longer, even up to 15 degrees. In either case, it was impressive. In binoculars it gave an even more stunning view. Below is a wide field photo I took of the comet on July 20 taken with a tripod-mounted Nikon D-810 and a 28-300mm Nikkor zoom wide open for 10 seconds at iso 1000. No tracking was used. Click on it for larger image.

Comet C/2020 F3 NEOWISE 20 July 2020

This wide field show is a 10s exposure with 28-300mm lens on Nikon D810 iso 1000.

Desiring a closer look at the details in the comet’s tails, I needed to use a tracking system with higher focal length for better image scale. The best bet for such a large object is a wide field astrograph. I grabbed the Takahashi FSQ-106ED4X, a splendid modified Petzval refractor telescope, and placed it on a portable Losmandy G-8 mount, battery operated, for the field. Attached to this was a Nikon D-810a, the modified version of the 810, allowing more H-alpha light to shine through. Nikon made this camera deliberately for astro-imagers, but this comet doesn’t have a whole lot of H-alpha light to speak of.  I set the system to tracking the stars and had the comet imaged for 1-minute exposures throughout the night at iso 1000, f/5, FL-530mm. By the end of the evening, all the gear was coated in dew except the heated objective lens (phew!) and I had some 30GB of images to deal with.

Once home and slept, the arduous task of slewing through all the images began. There were so many! I culled off the ones that had interference from automobile lights, lasers from people nearby shining them at the comet, kids with flashlights, and airplanes passing through the field. I kept the rest, some 30 near-perfect images. An example here, an unedited 1-minute exposure:

Comet C/2020 F3 NEOWISE 20 July 2020

Unedited 1-minute exposure of the comet.

It’s a very nice image!  The issue is that there is still some vignetting to deal with and some image noise from the heat and readout of the camera’s chip. There is always inherent noise to any digital system, and the solution? Stacking those images together in a median and getting a much cleaner and sharper image. The process is time consuming and CPU intensive, but well worth the effort. Stacking also gets rid of any one-time events like satellite passes (keep reading for more) which streak across the frames throughout the night. Surprisingly there are many. The end result of all the processing is this image below. It pretty much presents a fine portrait of Comet NEOWISE. The dust tail certainly spreads widely throughout the frame, and the blue ion tail is more than evident.

Comet C/2020 F3 NEOWISE 20 July 2020

This was taken through a Takahashi FSQ-106ED4X telescope at f/5. iso 1000 with Nikon D-810a. This is a stack of 30, 1 minute exposures.

What about those satellites? Just how many are flying through all those images? Watch this video to see!

So many satellites!  If you go through this video frame by frame you will also see one frame that has two streaks from a nearby green laser pointer. Alas.

11
Jul

Comet C/2020 F3 NEOWISE the July 2020 Surprise

This has been quite a year. Now, add to this a bright new comet, and it gets a little better, yes? Comet C/2020 F3 NEOWISE: Named after the Wide Field Infrared Survey Explorer’s asteroid hunting mission [https://neowise.ipac.caltech.edu/], this comet has become visible to the unaided eye, and, for now, is a morning object rising just before the Sun in the northeast sky. By the week of July 13th, the comet will be more of an early evening object, and it should also be getting fainter as it heads both away from Earth and the Sun.

Weather here in New Hampshire is not forgiving to astronomers. In July we typically have high humidity and heat. Add to that some vertical temperature instability, and thunderstorms will be the rule followed by wet foggy mornings once dew point is reached. We did have one clear morning this week, and that allowed for some quick imaging of comet NEOWISE. Be sure to click on the images to see in larger format.

Equipment used:

  • Nikon D-810a with 28-300mm zoom lens at 150mm at f/3.5 and Optolong L-Pro light pollution reduction filter.
  • Nikon D-810 with 300mm telephoto at f/4.
  • Tripods with slow motion controls: untracked.

Those looking to spot the comet should bring with them a pair of binoculars and the information provided in this article from Sky & Telescope. Be sure to find a viewing location away from ground fog, and with a low horizon.  A Bright New Visitor: How to Spot Comet NEOWISE [https://skyandtelescope.org/press-releases/new-bright-visitor-comet-neowise/]

Comet C/2020 F3 NEOWISE Comet C/2020 F3 NEOWISE Comet C/2020 F3 NEOWISE Comet C/2020 F3 NEOWISE Comet C/2020 F3 NEOWISE Comet C/2020 F3 NEOWISE