8SE magnification limits with imager plus Barlow

[alcol620]

Hi folks

Another query from a newbie.

I have a Celestron 8SE scope and have acquired an imager that is said to be equivalent to an eyepiece around 5/8mm. The maximum useful magnification of the 8SE is 480. With a focal length of 2000mm the imager's magnification is somewhere between 250 and 400. Am I right in saying, if I add a 2x Barlow, these figures will double and if I use a 3x Barlow they will treble. The magnification using the Barlows will be above the useful magnification level for the scope what would be the effects of this. By adding the Barlows I was hoping to get more light onto the imager pixels. ie a larger image.

Help much appreciated, thanks.

[Cornelius Varley]

Try not to confuse visual magnification with imaging scale, there is no magnification. The reference to a camera's eyepiece equivalent is only intended a guide to the field of view of a camera and not a true magnification (if you use a camera with a larger sensor the only thing that changes is the scale of the image). For lunar and planetary imaging the ideal focal ratio usually works out to be about f20 - f25 depending on the camera (sometimes you can push this a bit more).

[alcol620]

 Cornelius Varley thanks for the reply. Does that mean I can use a 3x Barlow with no problems. My imager is as seen on http://www.ebay.co.uk/itm/Solar-System-CCD-Astronomy-Imaging-Photography-Set-/380827149668?ssPageName=ADME:L:OC:GB:3160

[Cornelius Varley]

A 2x barlow would be better, but you should be able to use the 3x in good conditions.

[alcol620]

Thanks Peter

[ollypenrice]

Just to add to Peter's point about magnification, in visual observing there is something being magnified. It is the image on the retina. In photography there is no equivalent.

Olly

[michael.h.f.wilkinson]

For planetary imaging on a C8 (same optics as the 8SE), I tend to use a 3x Barlow on Mars, a 2.5x on Jupiter, and 2-2.5x on Saturn. This works quite well on a variety of planetary cameras (from "lowly" webcam to DMK or ASI planetary cameras). Some people have been using F/40 (4x barlow) on Mars with great success. Using the plain F/10 leads to disappointingly small planetary images.