Join for FREE
It only takes a minute!
Zeiss - Always on the lookout for something special – Shop now

Welcome to BirdForum.
BirdForum is the net's largest birding community, dedicated to wild birds and birding, and is absolutely FREE! You are most welcome to register for an account, which allows you to take part in lively discussions in the forum, post your pictures in the gallery and more.

Please school me on the Pentax 65

Reply
 
Thread Tools Rate Thread
Old Saturday 8th September 2018, 00:05   #1
justabirdwatcher
Registered User

 
Join Date: Sep 2014
Location: TX
Posts: 543
Please school me on the Pentax 65

Very experienced with binoculars, but fairly inexperienced with spotting scopes. My personal scope up to now has been an old Bushnell Spacemaster with a fixed 20x eyepiece. It is remarkably good, which is why I haven't bought a new scope in 20+ years. Everything I've compared it to has left me wondering why I need to spend $400+ on a new scope.

However, I have a keen interest in the Pentax, not only because of the rave reviews it receives but also because of the universal 1.25" eyepieces it uses.

Here's where I need help. I know literally nothing about 1.25" eyepieces. I've read a bit, and know that you don't necessarily have to spend a ton on an eyepiece to get a great image, but I don't know how to convert mm focal length to the convetional "power" setting, etc.

I do know I'm a fan of fixed focal length eyepieces. My 20x eyepiece on my Spacemaster blows any variable eyepiece I've ever seen out of the water in clarity and FOV. So I guess my question is, what eyepiece should I be looking at for the Pentax 65 that will give me 20-25X and not break the bank?

Thanks in advance for your help!
justabirdwatcher is offline  
Reply With Quote
Old Saturday 8th September 2018, 17:28   #2
jmepler
It's just a flesh wound.
 
jmepler's Avatar

 
Join Date: Sep 2007
Location: Pennsylvania
Posts: 1,218
To calculate magnification, divide the focal length of the scope by the focal length of the eye piece.

Conversely, to solve for eye piece focal length, divide the scope focal length by the desired magnification.

The focal length of the PF-65ED is 390mm. So, for 20X take 390mm/20x = 19.5mm eye piece focal length.

The Pentax XW eyepieces are fantastic (and waterproof, most astro eye pieces aren't), and there is an XW-20 available. Not cheap, but good deals on used eye pieces can be found.
__________________
Latest lifer: #373 Barrow's Goldeneye
Latest Pennsylvania lifer: #340 Western Meadowlark
Latest Lancaster County lifer: #302 Tricolored Heron
Use eBird to record your bird sightings.
jmepler is offline  
Reply With Quote
Old Saturday 8th September 2018, 17:56   #3
justabirdwatcher
Registered User

 
Join Date: Sep 2014
Location: TX
Posts: 543
Thank you. Any recommendations on 1.25" astro eyepieces that will give me a 25X ?
justabirdwatcher is offline  
Reply With Quote
Old Monday 10th September 2018, 13:22   #4
jring
Registered User

 
Join Date: Aug 2015
Location: Germany
Posts: 2,030
Hi,

quite frankly, if you have a scope that is doing 20x well (which is not very difficult) and you only want/need 20x, there is not really a need to upgrade.

Regarding the EP question for the Pentax with a body focal length of 390mm we get 390mm / 20 = 19.5mm or 390mm / 25 = 15.6mm. My recommendation would be to get 30x though - 390mm / 30 =13mm. You will not find astro EPs with the exact focal length - get sth in the ballpark and divide body fl by EP fl for magnification. You want to get wide angle EPs from 60 deg apparent field of view onwards.

Also be prepared to find out that a 3rd party EP you get will not come to focus in your Pentax spotter - they have a lot less focus travel than real astro scopes after all. So either find some friends with astro scopes and EPs to try theirs (the local astro club is a good idea) or get them from a shop with a no questions asked return policy.

Joachim
jring is offline  
Reply With Quote
Old Monday 10th September 2018, 15:13   #5
justabirdwatcher
Registered User

 
Join Date: Sep 2014
Location: TX
Posts: 543
Thank you for the response.

I have decided to go with the smaller and lighter Nikon 50 ED.
justabirdwatcher is offline  
Reply With Quote
Advertisement
Reply


Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is Off
HTML code is Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Pupils at Paget Primary School joined world's biggest school wildlife survey (RSPB) BF Newsroom Latest news from the RSPB 0 Sunday 8th February 2015 14:33
Pupils at Paget Primary School prepare to join world's biggest school wildlife survey BF Newsroom Latest news from the RSPB 0 Wednesday 28th January 2015 10:45
School bell rings to mark the start of world's biggest school wildlife survey (RSPB) BF Newsroom Latest news from the RSPB 0 Sunday 26th January 2014 12:08
School bell rings to mark the start of world's biggest school wildlife survey (RSPB) BF Newsroom Latest news from the RSPB 0 Sunday 19th January 2014 23:15
Current Classic "Old School" vs. Current State of the Art "New School"- Habicht vs SV stephen b Binoculars 50 Friday 26th July 2013 20:51

{googleads}

Fatbirder's Top 1000 Birding Websites

Help support BirdForum

Page generated in 0.17435288 seconds with 17 queries
All times are GMT. The time now is 22:59.