Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

sgl_imaging_challenge_banner_solar_25_winners.thumb.jpg.fe4e711c64054f3c9486c752d0bcd6f2.jpg

Ignoro

Astromaster 90/1000 diagonal

Recommended Posts

My friend has an Celestron astromaster 90/1000 refractor, do you think he'd benefit from getting a bst Starguider prism diagonal over the stock?

He observes planets from his balcony.

Thanks

Edited by Ignoro
  • Like 1

Share this post


Link to post
Share on other sites

I have the same erect-image diagonal that comes with that kit...

751994698_CelestronAmici2.jpg.32ce7585a2efcce83513b7b50a7e82c1.jpg

It's primarily for daytime/terrestrial use; birds in trees, ships at sea, that sort of thing, and during the day.  It can be used at night, but on the brighter objects, such as Jupiter, an illuminated line generally appears streaking across the face of the planet... 

5ufVAEI.jpg

What your friend needs for astronomical use, at night, is a STAR-diagonal.  I searched online for a "bst Starguider prism diagonal", and came up empty, but here are some star-diagonals for examples...

A star-prism... https://www.astroshop.eu/diagonal-prisms/celestron-zenith-prism-90d-1-25-/p,7987

A star-mirror... https://www.astroshop.eu/diagonal-mirrors/omegon-mirror-star-diagonal-90d-1-25-/p,46713

There are many others out there, and at varying levels of quality and price-points.  Simply ensure that the listing states "STAR" and "90°" within the description, and you can't go wrong.

Edited by Alan64
  • Like 1

Share this post


Link to post
Share on other sites

He'll be buying a BST starguider 8mm eyepiece, so maybe make just one order for 2 items from the same seller to save some shipping:

prism:
https://www.ebay.com/itm/Starguider-1-25-90-degree-prism-star-diagonal/382690001566?hash=item591a1a029e:g:sl8AAOSwIr5cH7VI

mirror:
https://www.ebay.com/itm/Starguider-1-25-90-degree-mirror-star-diagonal/163447486682?hash=item260e3ab8da:g:IG8AAOSwwhxcH6fQ

I looked through his scope a few days ago and didn't notice a line on planets.
I have a reflector so I'm unfamiliar with diagonals, is prism better then mirror? Would he see any difference in his scope?

Thanks

Edited by Ignoro

Share this post


Link to post
Share on other sites
3 minutes ago, Ignoro said:

He'll be buying a BST starguider 8mm eyepiece, so maybe make just one order for 2 items from the same seller to save some shipping:

prism:
https://www.ebay.com/itm/Starguider-1-25-90-degree-prism-star-diagonal/382690001566?hash=item591a1a029e:g:sl8AAOSwIr5cH7VI

mirror:
https://www.ebay.com/itm/Starguider-1-25-90-degree-mirror-star-diagonal/163447486682?hash=item260e3ab8da:g:IG8AAOSwwhxcH6fQ

I looked through his scope a few days ago and didn't notice a line on planets.
I have a reflector so I'm unfamiliar with diagonals, is prism better then mirror? Would he see any difference in his scope?

Thanks

No, that is not a star-prism diagonal within the first listing.  Read the fine print below.  It states "correct image", which means it won't be any different from the one he already has.  That seller is "incorrect" in stating that it's a star-diagonal.  I'll be contacting that seller.

The star-mirror diagonal within the second listing is a star-diagonal, and for use at night.

A star-prism is more durable, and for a lifetime.  A star-mirror is more prone to arriving out of collimation, alignment.  Also, mirrors scatter more light than a prism, resulting in a faint cloud of light surrounding brighter objects.

But if it has to be between those two, get the star-mirror, absolutely.

Share this post


Link to post
Share on other sites

Better getting a better quality mirror diagonal. This one has reasonable build quality. Not a high grade mirror in it but still up to the job.

Have used this one and it was not bad at all.

https://www.ebay.co.uk/itm/Opticstar-1-25-Deluxe-Diagonal-UK/322821924245?hash=item4b29afa595:g:5usAAOSw9XhZ3zMZ

Edited by johninderby

Share this post


Link to post
Share on other sites
27 minutes ago, johninderby said:

Better spending a little bit more for a reasonable quality mirror diagonal. This one has good build quality as well as a brass compression ring to clamp the eyepiece not just a screw. Not a high grade mirror in it but still up to the job.

https://agenaastro.com/gso-1-25-90-refractor-mirror-star-diagonal.html

The OP is in Croatia.  Is his friend in the U.S.?  He did list U.S.-based eBay listings within his post, however the seller is located in the UK.

EDIT:  I see that you corrected that.  Carry on.

Still, wouldn't a star-prism be more suitable for a longer-focus achromat?

Edited by Alan64

Share this post


Link to post
Share on other sites

I'm in Croatia and seller is UK :) just accidentally I put ebay.com, so you say he should get a prism but not the one from Starguider?

Share this post


Link to post
Share on other sites
1 hour ago, Ignoro said:

I looked through his scope a few days ago and didn't notice a line on planets.

Perhaps they weren't very bright at the time, but you'd eventually see it.  Look here...

333320394_Amiciline2b.jpg.2ee88251149a788eff168a7407201b1e.jpg

...that vertical line in the centre.  If it's illuminated enough, it'll show up, like when Jupiter's riding high in the sky and shining bright.  You'll see, and as I've seen it.

Star-diagonals have larger light-ports, and ideal for use at night when you need all the light you can get from an object.  During the day,  it doesn't matter if the port is small, like with those Amici, erect-image diagonals, for there's plenty of light with the Sun shining...

449071453_diagonaltypes3.jpg.aef6d1bca271dd2b433675d79d882f35.jpg

Share this post


Link to post
Share on other sites
8 minutes ago, Ignoro said:

I'm in Croatia and seller is UK :) just accidentally I put ebay.com, so you say he should get a prism but not the one from Starguider?

No, do not get that Starguider erect-image Amici-prism diagonal.  The listing states, "We are delighted to offer for sale this Starguider 90 degree prismatic correct image star diagonal", and "Another consequence of using this particular diagonal is that the prism produces the image in the same orientation as seen by the eye and so it will be the right way up and the right way round."

That one would be no different from the one your friend has now.  Again, both are primarily for daytime/terrestrial use.

https://www.teleskop-express.de/shop/product_info.php/info/p2484_Celestron-1-25--90--diagonal-prism-for-refractors-and-cassegrains.html

I really cannot recommend ordering a diagonal off of eBay, especially if you're unsure about diagonals.

Share this post


Link to post
Share on other sites

Now I understand the difference between diagonals. eBay is cool if you are moderately careful :)

I have something going on right now so I'll look into it in a few days,  thanks for your help, as always :)

Share this post


Link to post
Share on other sites
14 hours ago, johninderby said:

No problem buying off eBay if you are buying from a proper dealers eBay shop or you could buy direct from their bricks and mortar shop.

http://www.opticstar.com/Run/Astronomy/Astro-Accessories-Telescopes-Opticstar.asp?p=0_10_5_1_8_201

That star-mirror appears to be a good if not a great value.  Incidentally, their eBay shipping-policy excludes Croatia, but not within their home website; odd, that.

Share this post


Link to post
Share on other sites

You should note that the Opticstar is an all metal bodied construction with decent nosepiece and eyepiece holder. Good mechanical build quality. Almost all at that price point are just lightweight moulded plastic bodies and cheap nospiece and eyepiece holders.

Edited by johninderby

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.