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So you want to buy a telescope
- 1. So, You Want to Buy a Telescope? Why all telescopes suck Mark Casazza January 2021
- 2. REALLY? ALL TELESCOPES SUCK? Indeed, every telescope is a compromise. The challenge is to understand what you want and what compromises don’t affect you. • Portability • Size • Weight • Clean crisp views • Light gathering • Magnification • Ease of use • Ease of setup • Need for power • Need for external computing • Need for high end eyepieces • Ability to do photography • Unrealistic expectations • Cost • For many a Schmidt Cassegrain design is the ultimate compromise, but • Not the least expensive product • Ill suited for photography • A good starter scope is frequently a Newtonian reflector, but • What kind of mount matters • What to try you hand at astrophotography • Equatorial mount is a must • Refractor is probably your best bet • They also make reflectors specifically for photography • Many other items also need to be acquired
- 3. WHAT YOU WILL LEARN TODAY Relative newbie (1st, 2nd, or 3rd telescope) • What you need to think about before your next purchase. • The strengths of each design. • The problems with each design. • Eyepieces, oh my! Experienced mentor • Questions I have asked. • How to guide someone to the right scope for them, not the scope you would buy. • Hopefully, a few new things too.
- 4. QUESTIONS I ASK • What do you want to look at? • How much time and effort are you willing to spend to set up every night? • How much are you willing to learn? • Where do you plan to observe? • Where do you plan to store the scope? • How much can you carry and for how far? • How big is your transport vehicle? • Is this for visual, photography, or both? • What is your budget?
- 5. WHY THESE QUESTIONS MATTER • What do you want to look at? • Planets – Refractor with no central obstruction • Double stars – Refractor • Galaxies & Nebula – Large aperture • How much time & effort are you willing to spend to set up every night? • < 5 minutes – Dobsonian • < 20 minutes – Can add most fork mount go-to scopes • < 1 hour – Just about anything If you don’t use it, it is useless
- 6. WHY THESE QUESTIONS MATTER • How much are you willing to learn? • EQ mounts are not 2nd nature • Go to mounts require aligning • Star hopping is a developed skill • Computer/phone interfaces can be a challenge • Where do you plan to observe? • If it is not at home transport and weight come into play • If at home light pollution limits a large scope’s capabilities
- 7. WHY THESE QUESTIONS MATTER • Where do you plan to store the scope? • Portable or permanent • If you must carry it to set it up, how far? • Can you store it assembled? • How much can you carry and for how far? • 11” SCT’s can be a challenge to carry much over 30 feet! • Large dobs and just plain HEAVY
- 8. WHY THESE QUESTIONS MATTER • How big is your transport vehicle? • If the tube does not fit in your car… • That big dob looks great; hope you have a SUV • What is your budget? • It all comes down to money • Don’t forget the eyepieces. You need a minimum of 4 • 40mm • 20mm • 10mm • 5mm
- 9. WHY THESE QUESTIONS MATTER • Photography??? • Just cell phone shots? • Serious astro-photography • Requires EQ mount • Probably want a triplet if budget supports it • Need to save money for: • Computer $500 • Camera $500 to $2,000 or more • Software $500 • Filters – Ouch! • Guide scope and camera $500 • You need to learn a LOT
- 10. SO, YOU WANT… • High magnification • So you can see small objects and details • Large aperture • So you can see dim things • Pristine views of planets and no spikes on stars • No central obstruction • Able to be uses for photography too • Got it! • Call University of Chicago and ask about the Yerkes telescope
- 11. SO YOU WANT… • 40” & 24” refractors • Largest refractor in the world! • Not exactly portable • Probably not on budget either • Building is in a state of disrepair • Did I mention the $8,000,000 price? • Local light pollution
- 12. TYPES OF MOUNTS • Equatorial • German EQ • Open Fork or Wedge mounts • Equatorial Platform (Wedge for a Dobsonian) • Alt Az • Dobsonian • Fork
- 13. EQUATORIAL • Moves like the stars, not like we think • Point it at Polaris and 1 motor at 1 rate will track the stars • Just about a necessity for photography • Newbies almost never set them up right • If they are not pointed at Polaris, they are pointless! • Some home-made solutions are just plain dangerous! • Platformed Dobsonian anyone? • Are not easy to use.
- 14. CLUB EQ SCOPES
- 15. ALT(ITUDE) AZ(IMUTH) • Works like we think: • Up down • Left Right • But not like the stars move • Circle around Polaris • Resulting in: • The need for more built-in brains to track an object • The tracking rate in Alt and Az will vary by location in the sky • Long exposure photography reveals the field is actually rotating!
- 17. TYPES OF OPTICS • Refractors/Dioptrics • Doublets (Achromatic) • Triplets (Apochromatic) • Reflectors/Catoptrics • Newtonian • Cassegrain • Ritchey Chretien • Hybrid/Catadioptric (both refracting and reflecting) • Schmidt Cassegrain • Maksutov Cassegrain • Schmidt Newtonian https://en.wikipedia.org/wiki/List_of_telescope_types
- 18. LOCOMOTION • Full manual • Just the scope and your eyes • Push to • Manual setting circles (can be a DYI project for a manual scope) • Declination and Hour Angle (Equatorial mounts have these) • Digital setting circles (DSC) (Move till you see the coordinates you want) • Push to with tracking • Need DSC • Must do a star align • Go To (with tracking) • Must do a star align • Drop & Go (StarSense) • Scope does it all • Put it down, turn it on, wait, and look • Most expensive I’d rather pay for the optics. It comes down to priorities
- 19. DON’T FORGET THE EYE PIECES • Kellner (3) – 40 to 50 (planetary) • Free with your new scope • 3 for $73 • Plossl (4) – 40 to 52 (generally 52) • Surplus Shed – $24 to $29 • Orion – $35 to $99 • Televue – $96 to $116 • Explore Scientific – $80 to $130 • Erfle and related (5) – 60 to 70 (generally 68) • TPO Superview – $45 to $70 • Televue Panoptic – $250 to $526 • Not an Erfle • Explore Scientific – $180 to $390 https://en.wikipedia.org/wiki/Eyepiece • Nagler (8 or 9) 82 • Meade UltraWide • $130 to $ 250 • Explore Scientific 82 • $200 to $370 • Teleview Nagler 82 • $321 to $666 • Nagler “Plus” – Exotic glass • Teleview Ethos (8) 100 to 110 • $590 to 854 • Explore Scientific 100 • $450 to $1000 • Explore Scientific 120 • 9mm only $1,000 • Delos – 72 and long eye relief $352
- 20. MY JOURNEY • Winter 2001 – Using Tasco 7 X 35 binoculars, found Andromeda!!! • Spring 2002 – 10 X 50 Meade Binoculars (Damaged – discarded) • Spring 2002 – Discovery 8” full manual Dob (Sold) • Fall 2002 – Added Manual setting circles • Fall 2004 – Used Celestron NexStar C11 GPS • Summer 2008 – Personal Solar Scope • Fall 2008 – Used Orion EQ1 mount (Sold) • Spring 2010 – Meade DSI Pro camera • Fall 2010 – Used Full Spectrum Canon T1i camera • Spring 2011 – Used Orion Short Tube 80 • Spring 2011 – First pictures I saved (C11 & ST80) • Summer 2011 – First good picture EQ1, Canon, & camera lens • Spring 2012 – Used Atlas EQ-G • Spring 2012 – Used Celestron GP-C102 (Sold) • Fall 2012 – Started to guide • Fall 2013 – Explore Scientific ED-127 • Fall 2013 – Used Pentax 20 X 60 Binoculars • Fall 2019 – Used Star Master f/4.5 20” • Winter 2020 – ZWO ASI26000MC camera
- 21. TRIVIA QUESTION • What makes this a BAD scope? • Rickety mount • Difficult to move and lock in position • Provided eyepieces are too powerful • Huygen – 40 field of view • 4mm – 175X (Maximum useful magnification is 120X) • 12.5mm – 56X (Actually aligns with Best General Viewing at 48X) • Sun filter! • Long focal length 700mm • Limited field of view (13.7’ & 42.9’) • Hard, if not impossible, to find an object! • Who bought this as their first scope?
Editor's Notes
- Who in the room has been asked to help someone pick a telescope? We are all biased by our own experience, good or bad.
- If you have been in this hobby for any time you know every telescope has a weakness. Let’s look over my list Did I miss anything?
- If I’m doing my job, everyone will learn something
- I always ask budget last I try to ask questions that have no obvious right answer
- I ALWAYS discourage anyone from getting into photography until they have at least spent a year doing visual observing. Media it pushing people right into photography. It seems just as much a hobby killer as those cheap scopes.
- This seems like a trivial choice, but reality is the mast majority of first scopes that are equatorial will never be set up right. That’s right, NEVER
- Why are these EQ scopes: PST, grab and go with no alignment stars can track I see lots of cameras on these scopes
- Much more approachable for anyone, especially a newbie
- Funny, no cameras
- Refractors No central obstruction – perfect for planets, but without a triplet you will see the color distortion Limited light gathering power max 6” Reflectors Can get very big. I’ve looked through a 36” Great at gathering light Central obstruction and vanes puts refraction spikes on stars The too can get long Hybrids Focal length is much greater than focal length = tremendous magnification Don’t get much bigger than 14” Largest central obstruction, focus tends to be soft
- The more tech the more money you are spending on the tech If the person is willing to learn the sky the full manual is the way to go, the next scope can be a goto
- You can spend more money on Eps than the scope Fast scopes demand better EPs