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What to expect Explorer 150P


Pryce

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Hey yall!  It's me asking stupid questions again! 

 

So I couldn't wait starting with imaging so I've ordered a EQ6-R Pro. I already have a 150P and I'm going to move the mirror up the tube for prime focus.

 

So my first question,  how far do I have to move the mirror up the tube to reach prime focus with a DSLR?   I've already ordered an adapter so I can connect the T adapter on the drawtube itself(ie. No EP holder and barlow)

 

And my second question, what can I expect from a 150P without a barlow in terms of imaging?  Does anyone know of (or have) any photos taken with a similar setup? 

 

Edited by Pryce
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If you just start out with imaging, I would remove the barlow from the setup. This will only complicate things. Add it later (if you still want to), once you are familiar with the capabilities and limitations of your gear. As for reference images, check astrobin.com. The search engine should provide you with examples.

good luck, and have fun

Edited by wimvb
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On 26/08/2020 at 08:53, Pryce said:

to reach prime focus with a DSLR

Use long m5 bolts to move the mirror up the tube say 5mm at a time. I think 15mm should do it. You may want then to cut the tube to make it permanent BUT... if at any stage you contemplate using the sw 0.9cc then add 1cm to whatever value you obtain. You'll also need longer springs or someone with a steady hand to push the primary against the adjusting nuts (remove the knurled adjusters) whilst you test focus.

Remember though that the secondary mirror will be too small to cover aps-c. Although flat frames may help, you may want to consider the 130pds instead. A lot less hassle;)

 -  https://www.astrobin.com/gear/14728/skywatcher-explorer-130p/

Cheers and HTH

 

 

 

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Doesn't the 150P come to DSLR focus by unscrewing the eyepiece extender and attaching an adaptor as already purchased by the op? Removing the eyepiece extender brings the camera closer to the mirror. Same as on my 150PL. Not sure if it would work with a CC added though.

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12 minutes ago, bobro said:

Doesn't the 150P come to DSLR focus by unscrewing the eyepiece extender and attaching an adaptor as already purchased by the op?

Hopefully!  It'll bring the camera much closer to the focuser.   So we'll see once it arrives!

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1 hour ago, alacant said:

Remember though that the secondary mirror will be too small to cover aps-c. Although flat frames may help,

You lost me here unfortunately. Can you elaborate?

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5 hours ago, Pryce said:

Can you elaborate?

Hi

The primary mirror makes a cone of light. Moving the primary closer to the secondary will cause the cone to be fatter at the position of the secondary;  not all the primary light is caught by the secondary. Hence the larger secondary on the 130pds which is supplied with a secondary to collect all the light, despite the shorter tube.

HTH

 

Edited by alacant
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22 minutes ago, alacant said:

Hence the larger secondary on the 130pds

I see.   So basically I should just forget converting my 150P to a PDS and rather just buy abother PDS OTA instead? 

 

Unless the adapter I've bought works as intended and I don't have to move the primary mirror of course.

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Do you have a coma corrector? Pds or not you need one and depending on which one you get this can shift the focus position even more.

I wouldnt move anything until you have it all assembled.

I can easily reach focus with my 150p but the drawtube protrudes into the light path and eats a chunk out of the stars. The solution to this was chopping a bit off the drawtube.

 

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1 minute ago, jimjam11 said:

Do you have a coma corrector? Pds or not you need one and depending on which one you get this can shift the focus position even more.

I wouldnt move anything until you have it all assembled.

I can easily reach focus with my 150p but the drawtube protrudes into the light path and eats a chunk out of the stars. The solution to this was chopping a bit off the drawtube.

 

No coma corrector yet,  and yeah, I heard the drawtube might need to get shortened down but that's a very minor adjustment as far as I understand

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15 minutes ago, Pryce said:

just buy abother PDS OTA instead? 

Nooo. You gotta have a go first!

E.g. the 200p will focus a DSLR with a 1.0x cc. Just not with the 2 element SW cc.

 

Edited by alacant
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Just now, alacant said:

Nooo. You gotta have a go first!

 

Oh of course!  I'll try making it work without major adjustments first,  but if the P versions has a smaller secondary that the PDS versions as mentioned above and moving the primary mirror up the tube isn't an optimal solution, I might just "make the best of it" with the 150P for now and then save up for a 200 or 250 PDS

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3 hours ago, alacant said:

E.g. the 200p will focus a DSLR with a 1.0x cc. Just not with the 2 element SW cc.

Hmm.  The 2 element SW cc is that the same as the 0.9x SW CC? 

 

Would you mind giving me an example of a CC that works well with my setup? 

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5 hours ago, Pryce said:

I see.   So basically I should just forget converting my 150P to a PDS and rather just buy abother PDS OTA instead? 

 

Unless the adapter I've bought works as intended and I don't have to move the primary mirror of course.

I wonder whether the secondary mirror of a 150 PDS is available from SW as a spare part that can be employed to get around this issue. However, the position of prime focus and secondary mirror size aren't the only differences as the 150 PDS also has a reasonable 2-speed Crayford focuser. FWIW, I sometimes find it difficult to get focus in my DSLR with that and suspect it would be worse with the R&P focuser of a 150P.

I note that SW Explorer PDS reflectors have come down in price at FLO since I bought my 150 PDS (£229 for the 150 and £176 for the 130 at time  of writing), which makes me wonder whether the conversion makes financial sense. That said, tinkering with adaptations always makes sense from a 'blokes in sheds' perspective!

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30 minutes ago, Geoff_L said:

which makes me wonder whether the conversion makes financial sense.

Indeed, that's what I'm thinking as well.  I had already ordered a automatic focuser from FLO, which I believe should get me around the dual speed focuser issue.  And moving the primary mirror up the tube would be an easy task with longer bolts and springs to hold the mirror in place,  but now that it turnes out I need a bigger secondary mirror as well, I'm honestly thinking it would be smarter to cancell my order for the automatic focuser (for £45 and that hasn't been shipped yet), sell off my 150P and instead just buy myself a 200P-DS!



 

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