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About Rocket_the_Raccoon

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  1. Rocket_the_Raccoon

    Eyepiece Beginner Advice

    The Skywatcher 8-24mm is pretty good according to http://astro-okulare.de/English/indexe.htm I believe it is the same as the Celestron and Orion 8-24mm. It might even be under other brand names too. The drawback of course, as stated, is the narrow field of view at the 24mm end but you have a 25mm anyway. If you are into DIY and can obtain old compact binoculars at very low price (e.g. charity shops, items that collecting dusts at home, ...), you might want to consider making a 33mm eyepiece like what I did in:
  2. Good advice! I somehow forgot that I can also use my moon filter on Venus too.
  3. I place my 70mm f/13 (also an Astromaster) on an Orion version of CG-4...and I used the Astromaster AZ mount with my 70mm f/5.7 as a grab-and-go combo. My first telescope is a 50mm f/12 but it is a Tasco and I used to have a 60mm f/15 which gave superb views even at 150x. I loves long refractors, too bad they are not made (as least not within my budget) anymore.
  4. Rocket_the_Raccoon

    Eyepiece Beginner Advice

    Greetings, kingbo37. Your next purchase on eyepieces really depends on what are your intended observation targets. For planets, you needs on-axis sharpness, contrast, and brightness more than edge performance and field width. Thus, you could save some money by buying short focal length eyepieces of simpler designs (e.g. Abbe Ortho, Plossl, or even a Kellner). In fact, I strongly suggest you patiently wait for the best seeing (atmospheric condition) and try out your 10mm stock eyepiece, which I assume is If you don't mind the risk of disassembling it, darkening the lens edges should help enhancing the contrast which is essential in planetary viewing. On the other hand, a good 2x barlow is also a good investment for a short focal length telescope like yours. If you want a wider field than your 25mm can give to hunt for deep sky objects and to do wide field scanning, then you can go for a 32mm Plossl which gives you a field of ~0.45 degrees wider without spending a lot. The edge performance (sharpness, distortion, etc.) from a Plossl won't be first-class as you have a fast f/5 objective mirror. To get a wider field than this, you will need to go for a 2" eyepiece (I believe your scope has a 2" focuser) and it will be much more expensive. One thing worth noting is as your Newtonian has a central obstruction from the secondary mirror, there is a limit on the longest focal length eyepiece you can use but I do not know how to calculate this. Finally, enjoy your telescope and wishing you clear skies!
  5. Rocket_the_Raccoon

    DIY 6-Element 33mm Eyepiece

    Béla Szentmártoni (1931-88) was a Hungarian amateur astronomer and telescope maker. He founded the Albireo Amateur Astronomy Club in 1971 and have made one hundred mirrors ranging from 4" to 10". On the August 1967 issue of Sky and Telescope (http://alpha.dfmk.hu/~albireo/szm/skylap.gif), he published his making of a 6" rich-field Newtonian with an eyepiece design of his own, giving a TFOV of 1.5 degrees. The original Szentmártoni eyepiece formula consisted of 3 doublets, all with a focal length of 65mm. The spacing of the field group elements is 2mm while the spacing between the field group and the eye lens is 4mm. The modified version above retains the basic orientation of the 3 doublets and spacing ratio of 1:2. However, the focal lengths and actual spacings are different (as shown in the diagram). ( Further Info : https://hu.wikipedia.org/wiki/Szentmártoni_Béla , http://alpha.dfmk.hu/~albireo/szm/atm.htm ) Using the 3-lens formula from http://www.astronomyboy.com/eyepieces/ep_calc.shtml, the EFL of this modified version is 33mm. The TFOV is calculated by (field stop / objective focal length) x 57.3, which is then used to obtained the AFOV based on the EFL, AFOV = TFOV x (objective focal length / EFL of eyepiece). Finally, eye relief is calculated based on AFOV and the 7mm human pupil size using the formula from http://www.mira.org/ascc/pages/lectures/fabform.htm. For a 1.25" 33mm eyepiece, an AFOV of 43 degree is not considered wide in today's standard. However, one have to note that the AFOV of any eyepiece is limited by the size of its field stop and many 1.25" eyepieces in the 30~32mm range have smaller AFOVs than specified. For example, Baader Classic Plossl 32mm has an AFOV of ~47 degrees (https://stargazerslounge.com/topic/179005-baader-classic-32mm-plossl-meets-vixen-30mm-npl-plossl/) and the Skywatcher Super Plossl 32mm has an AFOV of 43 degree (http://astro-okulare.de/English/skysp32e.htm). As for image quality, this 33mm Modified Szentmártoni is not just sharp but also sharp to the edge without distortion on my f/5.7 refractor. I believe it will pretty much replace my veteran Omcon 25mm Plossl (Celestron silver-top equivalent. fully coated only) as a great finder eyepiece and an indispensable accessory to enjoy rich star fields. Ingredients : - two 25mm doublets with focal lengths of 100mm scavenged from a pair of 10x25mm compact binoculars - one 21mm doublet with focal length of 80mm scavenged from a pair of 8x21mm compact binoculars - plastic objective retention ring from the 10x25mm binoculars as the spacer of the two 25mm doublets (field group) - plastic part from the eyepiece of an old 10x50mm binoculars as the eyepiece top that holds the 21mm doublet (eye lens) - 1" copper pipe coupler as eyepiece outer barrel - metal ring from the StarPointer of a Celestron Astromaster 70AZ (intended to be the field stop, not used) - rubber eyecup from another eyepiece (not used) - rubber eyecup from an old pair of 10x50mm binoculars - chalkboard stickers to make the inner barrel of the eyepiece and for fitting elements with different diameters - E6000 crafting glue - black marker pen for darkening the edges of the doublets Lessons Learned : - Though the total time needed to build the eyepiece is less than an hour, I spilt it up to several days in order to let the E6000 glue fully dried. - When glueing a lens to a plastic part, the glue should be put on the edge of the lens, not the plastic, to avoid excessive glue spreading onto the lens surface. - The use of an internal eyepiece barrel enables more precise placement of the field group and avoids the mess of glueing the field group to the copper barrel. - The chalkboard sticker, which was rolled up to make the internal barrel, took out the need of painting the inside of the eyepiece with flat-black paint. My DIY Eyepiece Set : 33mm, 18mm, and 10mm
  6. Rocket_the_Raccoon

    Rocket's Album

    Kindergarten-level DIY and Astrophotography
  7. Just like LukeSkywatcher said, you need a moon filter for viewing the moon comfortably. As for Jupiter, I believe it was just bad "seeing" (atmospheric condition). Bad seeing can make planetary images blurry and featureless even on a telescope larger than yours. A few nights ago. I saw the clearest and sharpest view I have ever seen with my 70m at 111x. About half an hour before that, Jupiter was featureless at the same magnification.
  8. Congratulation! Your equatorial mount (a Celestron version of EQ-2) will give you far better slow motion capability than the Astromaster AZ mount. FYI, if you ever find the high power view from your 10mm eyepiece unsatisfactory, it might very possibly be the "ball-shape" diagonal to blame, not the eyepiece. I have a review on the Astromaster 70AZ which talks about this issue:
  9. Rocket_the_Raccoon

    need help

    It could be the barlow has increased the focal ratio of the telescope to a point that the H 20mm performed obviously better than on its own. When Christiaan Huygens designed his eyepiece in 1662, telescopes had far slower focal ratios than the f/10~f/15 of today's long archomatic refractors.
  10. Rocket_the_Raccoon

    Suggestions for a first scope

    No matter you are going for the "one scope for all" or "two scopes" appproach, I would suggest go for a portable short refractor (the ED80 mentioned in the replies) first. My point of view is a 80mm that got used a lot is better than an 8" sitting at home indoor. I have a short (f/5.7) refractor, a long (f/13) refractor, a light-weight alt-azimuth mount and an entry-level imaging equatorial mount. I found myself, using the short refractor more mainly because of its portability and ease of setup. For ocassional high magnification with the short refractor, I uses a Meade 3x barlow with my 10mm Plossl.
  11. Rocket_the_Raccoon

    Travel scope frac or mak?

    Celestron 70mm f/5.7 (Travelscope 70) Celestron 70mm f/12.9 (Astromaster 70)
  12. Rocket_the_Raccoon

    Travel scope frac or mak?

    How about using a 3x barlow with the wide-field refractor? Although I have a f/13 long refractor, I often use my f/5.7 refractor to do planetary observations with a Meade 3x and my Plossl 10mm.
  13. Rocket_the_Raccoon

    DIY 10mm Eyepiece and Performance Comparison

    Thank you! Almost all long 60mm refractors have above average objective lenses. I used to own a f/15 and I still remembered the view of the Trapezium at the heart of M42 at 150x with a 6mm Ortho. Also, I have a similar DIY ~18mm eyepiece like yours, scavanged from an old 10x50mm binoculars but mine is not wide field, possibly a Kellner. It actually has better edge sharpness than my Celestron 3-element 20mm (1-2 modified König) on my f/5.7 refractor.
  14. Rocket_the_Raccoon

    DIY 10mm Eyepiece and Performance Comparison

    Thanks and yes, I was surprised how well the eyepiece performs given its cost. I have also made a DIY 33mm but instead of scavanged from binoculars eyepiece, it was built from scratch with binoculars objective lenses. I am in the process of some final performance testing and will write up a post once it is done. I think some of the wide -field binculars use Erfle eyepieces too. Indeed! I treasure my DIY eyepieces despite their costs, it is the efforts and accomplishments that matter.

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